NRLF 


54 


CONCRETE 
REVIEW 


GERMAN  METHODS  IN 
PORTLAND  CEMENT 
MANUFACTURE 

DRY  AND  WET  PROCESSES 
By  DR.  OTTO  SCHOTT 


PUBLISHED  BY 

THE  ASSOCIATION  OF  AMERICAN  PORTLAND 
CEMENT  MANUFACTURERS-IANDTITLE  BLDG'PHILA- 

SUBSCRIPTION  50  CENTS  PER  YEAR  SINGLE  COPIES  SCENTS 


German  Methods   in  Portland    Cement 

Manufacture.    Dry  and  Wet 

Processes. 


BY  DR.  OTTO  SCHOTT, 

TECHN.  CHEMIST,  HEIDELBERG. 


Gentlemen:  Last  year,  when  seeking  information  concerning 
the  manufacture  of  cement  in  the  United  States  of  America,  I  had 
the  opportunity  of  inspecting  a  large  number  of  your  cement  works 
and  studying  American  equipment  and  methods  of  manufacture. 
The  impressions  I  gathered  are  probably  known  to  you  for  the  most 
part  from  the  publication  of  some  of  the  lectures  I  have  given  in 
Germany  and  Austria  on  the  subject.  Although  it  is  difficult  from  a 
mere  inspection  to  form  a  correct  picture  of  the  working  methods  of 
the  different  factories,  still  I  think  that  on  the  whole  I  have  correctly 
judged  the  American  Portland  cement  industry. 

To-day  I  want  to  give  you  a  picture  of  the  German  cement 
industry,  based  not  only  on  the  inspection  of  various  factories,  but 
also  on  an  experience  of  many  years  in  this  industry.  In  many 
respects  the  German  cement  industry  has  a  different  manner  of  work- 
ing from  the  American,  and  I  think  it  will  interest  you  all  if  in  my 
remarks  I  refer  particularly  to  these  divergencies.  I  think  that  in 
this  way  you  will  learn  more  than  by  visiting  different  factories  in 
Germany. 

Although  the  German  cement  industry  is  considerably  older  than 
the  American,  and  Portland  cement  was  manufactured  in  Germany 
more  than  fifty  years  ago,  the  total  production  has  to-day  only 
reached  the  figure  of  30,000,000  barrels,  which  are  made  in  about 
100  factories,  of  which  96  factories  are  united  in  the  Association  of 
German  Portland  Cement  Manufacturers.  In  comparison  with  the 
enormous  increase  of  the  young  American  cement  industry,  with  its 
production  of  73,000,000  barrels  last  year,  it  might  seem  that  the 
German  cement  industry  has  not  made  the  progress  it  ought  to  have 


M12991 


made.  But  you  should  bear  in  mind  that  Germany  is  only  a  small 
country,  not  even  as  large  as  the  State  of  Texas.  In  proportion  to 
its  area,  it  still  holds  the  first  place  with  its  cement  production.  You 
should  further  bear  in  mind  that,  partly  on  account  of  narrow- 
minded  building  regulations  and  partly  through  the  presence  of 
sufficient  quantities  of  natural  building  stone,  Portland  cement  is 
not  nearly  so  much  used  in  Germany  as  in  America.  The  Germans 
have  not  yet  engaged  in  the  use  of  cement  in  such  an  admirable 
manner  as  I  have  found  in  your  country.  As  regards  the  quality 
.•••.of  tbe.*  £ertje}it:  and  the  cost  of  manufacturing,  I  think  I  can  con- 
'•'scienttoilsly*  assert  that  Germany  is  ahead  of  many  countries.  With 


;•  ijje'iaj'l^  qv.erjDrotluction,  which  greatly  exceeds  the  demand,  the 
*  'ma'nufacturers  *w*ere  forced  to  manufacture  the  cement  as  cheaply 
as  possible,  and  constantly  to  improve  the  quality. 

I  will  first  give  you  a  picture  of  how  the  cement  works  are  dis- 
tributed over  all  Germany.  You  see  that  in  various  places  the 
factories  lie  close  together,  as  is  the  case  in  the  Lehigh  district 
or  in  Kansas.  If  you  bear  in  mind  that  the  area  of  Germany  is  not 
larger  than  the  States  of  Pennsylvania  and  New  York  together, 
and  if  you  also  consider  that  the  adjoining  countries,  as  Belgium, 
France,  Austria,  and  Switzerland,  also  produce  cement,  and  are  able 
to  import  it  free  of  duty  into  Germany,  while,  on  the  other  hand, 
the  countries  levy  a  high  duty  on  Portland  cement  from  Germany, 
you  can  then  form  an  idea  of  the  great  difficulties  with  which  the 
German  cement  industry  has  to  contend.  About  one-fourth  of  the 
cement  works  are  in  Rheinland  and  Westphalia,  where  they  are  as 
close  together  as  here  in  the  Lehigh  district.  The  proximity  of  the 
coal  mines  and  an  excellent  raw  material  have  favored  the  building 
of  so  many  works  in  one  spot.  Similar  groups  of  cement  works 
are  found  near  Hannover,  Hamburg  and  in  Silesia,  only  the  30  fac- 
tories situated  in  south  Germany  being  fairly  evenly  distributed. 
That,  with  this  large  number  of  factories  and  their  large  producing 
capacity,  the  German  cement  industry  still  prospers  to  a  certain 
degree,  is  to  be  attributed,  in  the  first  place,  to  the  formation  of  syn- 
dicates, which  fix  "  quotas  "for  the  various  factories  and  take  care 
that  no  more  cement  is  manufactured  than  can  be  sold,  and  which 
also  regulate  the  prices  by  fixing  minimum  prices  at  the  commence- 
ment of  each  year. 

We  have  at  present  in  Germany  five  syndicates,  the  oldest  and 
firmest  of  which  is  the  South  German  Cement  Syndicate,  which  was 
prolonged  last  year  until  the  year  1925.  Each  factory  is  given  a 


"quota"  in  proportion  to  its  producing  capacity,  and  it  participate 
in  proportion  to  its  " quota"  in  the  increase  in  consumption.  The 
sale  of  the  cement  is  done  through  a  central  office,  which  has  five 
further  sales-offices  under  it  to  facilitate  the  transaction  of  business. 
No  factory  can  sell  direct  to  the  consumers,  and  all  sales  must  be 
made  through  the  sales-offices.  The  sales  territory  of  each  syndicate 
is  carefully  defined  by  contract,  so  that  each  syndicate  may  only  sell 
within  a  definite  circuit  of  the  factories  belonging  to  it,  whereby 
large  economies  in  freight  are  made.  The  price  of  a  barrel  of  cement 
is  at  present  $1.00  to  $1.25. 

The  fixing  of  the  price  is  determined  so  that  the  smaller  factories 
belonging  to  the  syndicate  shall  have  a  normal  profit,  but  the  price 
of  foreign  cement  and  of  other  building  materials  has  also  to  be  con- 
sidered. 

It  would  certainly  be  wrong  to  assume  that  the  regulation  of 
prices  is  done  arbitrarily  for  the  sole  object  of  getting  the  highest 
possible  prices.  The  principal  merit  of  the  syndicates  is  that  they 
balance  the  production  of  the  factories  with  the  sale  of  the  cement. 
The  syndicate  in  Rheinland  and  Westphalia  operated  its  factories 
last  year  57  per  cent,  of  their  producing  capacity,  and  the  South 
German  syndicate  78  per  cent. 

The  syndicates  in  the  different  districts  of  Germany  are  connected 
by  agreements,  which  determine  how  far  each  factory  can  sell  in  its 
environs. 

Raw  material  for  Portland  cement  is  found  pretty  nearly  all  over 
Germany,  principally  limestone  with  shale,  and  it  frequently  has 
naturally  the  proper  combination  for  Portland  cement.  Such  de- 
posits you  will  find  in  south  Germany,  principally  in  Wurttemberg, 
in  the  Swabian  Jura,  around  Hannover  and  also  on  the  Rhine.  Some 
factories,  principally  in  central  Germany,  use  limestone  with  clay, 
which  is  mostly  very  damp.  The  cement  works  on  the  northern 
coast  around  Hamburg  and  Stettin  use  wet  chalk  and  clay  as  raw 
material  and  work  on  the  wet  process. 

Such  pure  limestone  as  is  used  for  cement-making  in  many  places 
in  America  is  not  met  with  in  Germany.  On  this  account  white 
Portland  cement  is  not  made  in  Germany  on  a  large  scale. 

The  quarry  of  a  German  cement  factory  presents  quite  a  different 
aspect  from  an  American  one.  The  steam-shovel,  which  is  found 
here  in  almost  every  cement  factory,  is  not  yet  used  in  Germany, 
as  the  factories  are  mostly  so  small  that  the  purchase  of  a  steam- 
shovel  would  not  pay.  Where  the  lime  stratum,  as  in  Westphalia, 


is  only  20  feet  thick,  the  stone  is  loosened  by  hand  and  shoveled  into 
the  cars.  Only  small  tip-cars  containing  about  1  square  yard  are 
used,  and  they  are  hauled  direct  into  the  factory  by  means  of  a  wire 
rope-way.  You  will  find  nowhere  in  Germany  such  large  locomotives 
as  are  customary  here  in  many  places.  The  wire  rope-way  and  the 
suspended  rail  are  preferred,  as  by  them  smaller  quantities  of  raw 
material  are  regularly  transported  to  the  factory  at  quite  even  inter- 
vals, and  can  then  be  tipped  direct  into  the  crusher  without  any 
interruption. 


Fig.  1. — Gallery- work.    Wall  of  Quarry  Prepared  for  Blast. 

When  the  limestone  strata  is  thicker,  i.  e.,  from  65  to  100  feet 
high,  the  so-called  "gallery-work"  is  applied. 

The  entire  wall  of  the  quarry  is  undermined  to  a  breadth  of  65 
to  160  feet  by  driving  single  horizontal  galleries  65  feet  long  into  the 
wall.  At  a  depth  of  33  feet  these  are  joined  together  by  a  cross- 
drift,  so  that  finally  the  whole  side  of  the  quarry  rests  only  on  single 
pillars  6J^  feet  high  and  6J^  feet  in  diameter.  Each  of  these  pillars 
is  then  bored  in  three  places  and  the  drill-holes  are  charged  with 
donarit,  dynamite  not  being  used  in  Germany  on  account  of  its 
dangerous  properties. 

4 


As  soon  as  the  so-called  "fall"  is  prepared,  the  charges  are  all 
fired  simultaneously  by  electricity,  the  pillars  are  all  blown  away  at 
the  same  time,  the  side  of  the  quarry  loses  its  support  and  falls  to 
pieces,  at  the  same  time  breaking  up  the  large  rocks.  The  material 
is  then  shoveled  into  cars  by  hand.  This  work  could  certainly  be 
done  profitably  by  one  of  the  steam  shovels  used  in  America,  and 
which  have  recently  been  introduced  into  Germany.  The  prepara- 
tions for  such  a  "blasting"  take  up  months,  but  the  material  loosened 
and  broken  up  in  this  way  lasts  for  months,  and  while  it  is  being 
loaded  off  and  worked  up,  preparations  are  made  for  the  next  blast- 


Fig.  2. — Gallery-work  after  the  Blast. 

ing.  The  heap  of  material  you  see  here  contains  50,000  square  yards, 
and  sufficed  for  the  making  of  300,000  barrels.  This  way  of  quarry- 
ing has  many  advantages :  above  all  things,  all  danger  to  the  workmen 
is  eliminated,  as  they  do  not  need  to  climb  about  the  steep  sides  of 
the  pit.  All  work  is  done  at  the  bottom  of  the  pit.  A  fairly  uniform 
mixing  takes  place  in  the  pit  by  the  rock  all  falling  down  together. 
The  layers  rich  in  clay  are  mixed  with  those  rich  in  lime. 

A  disadvantage,  however,  is  that  with  frequent  rains  the  heap  of 
material  often  gets  wet,  and  the  drying  is  rendered  difficult.     On 

5 


this  account  some  cement  works  in  Germany  have  recently  intro- 
duced the  glory-hole  method.  At  the  foot  of  the  quarry  a  single 
passage  100  to  130  feet  deep  is  driven  into  the  quarry  side,  and  from 
the  end  of  the  same  a  shaft  is  bored  straight  upward,  until  the  surface 
is  reached.  At  the  foot  of  this  shaft  there  is  fitted  a  horizontal  door 
sliding  on  rails,  which  can  be  opened  and  shut  by  means  of  a  lever. 
They  then  start  to  widen  the  top  of  the  shaft  funnel-shape  by 
loosening  the  material  around  the  shaft  and  letting  it  simply  roll  down 
to  collect  on  top  of  the  closed  sliding  door. 


Fig.  3. — Floor  of  Quarry  with  Passage  for  Glory-hole  and  Wire  Rope-way. 

The  wire  rope-way  is  brought  right  up  to  this  slide,  the  cars  are 
run  under,  the  slide  opened  until  a  car  is  filled  and  then  closed.  The 
full  car  now  runs  automatically  on  the  wire  rope  into  the  works. 
Such  a  glory-hole  yields  with  four  men  (two  up  above,  two  down 
below)  300  square  yards  of  material  in  a  twelve-hour  day.  The 
benefit  of  this  method  lies  in  avoiding  the  picking  up  of  the  material 
with  the  hand  or  steam  shovel,  and  at  the  same  time  it  has  the  ad- 
vantage of  safety  and  of  blending  the  different  layers.  Besides, 
in  rainy  weather  the  water  runs  off  down  the  steep  sides,  so  that 
the  material  keeps  dry.  Boring  is  generally  done  with  compressed 

6 


air  and  small  boring  machines,  similar  to  those  you  have  here  in 
America. 

As  I  have  already  remarked,  the  material  forwarded  by  wire  .rope 
or  suspended  monorail  direct  into  the  works  is  tipped  direct  into  the 
crushing  machinery.  Unlike  America,  the  Blake  crusher  is  still 
preferred  in  Germany,  and  the  Gates  crusher  is  very  seldom  met 
with.  If  the  material  is  not  so  hard,  the  so-called  crushing- worm 
is  often  used.  The  same  consists  of  a  thick  shaft  provided  with 


Fig.  4. — Car  being  Filled  from  the  Glory-hole  through  the  Sliding  Door. 


grooves,  which  rotates  between  horizontal  bearings  inside  a  casing 
lined  with  steel  plates. 

For  drying,  the  Cummer  rotary  drier  is  much  used  in  Germany. 
In  general,  the  German  rotary  drier  has  a  much  smaller  diameter 

7 


than  the  American,  usually  only  39  inches.  In  America  coal-dust 
has  been  applied  in  recent  years  for  heating  the  rotary  driers,  an 
arrangement  which  the  Portland  Cement  Works  of  Heidelberg  and 
Mannheim  introduced  twelve  years  ago  in  all  their  works,  except 
that  there  was  built  in  front  of  the  cylinders  a  chamber  with  grating 
in  which  the  firing  took  place.  It  has  been  proved  that  with  the  use 
of  coal-dust  the  drying  of  the  raw  material  is  much  more  thorough 
and  the  coal  consumption  less. 


Fig.  5. — View  from  Top  of  Glory-hole.    The  Material  is  Loosened  and  Rolls  down 
before  the  Closed  Sliding  Door. 


I  should  like  to  make  mention  here  of  a  special  rotary  drier,  with 
which  the  utilization  of  the  hot  gases  is  profitably  increased  by  the 
division  of  the  inside  of  the  cylinder  in  separate  cells.  By  this 
means  a  more  uniform  distribution  of  the  material  in  the  interior 
of  the  cylinder  is  obtained,  and  the  surface  is  also  increased,  which 
facilitates  the  drying.  With  very  wet  material  there  is  naturally  the 
danger  of  some  of  the  cells  getting  blocked  up,  but  for  drying  coal  a 
more  ideal  rotary  drier  cannot  be  imagined. 

With  such  a  drier,  6  feet  6  inches  in  diameter  and  33  feet  long, 
180  tons  of  rather  small  moist  coal  are  daily  dried  at  Heidelberg. 

8 


For  grinding  the  raw  material  the  same  systems  of  mills  are  used 
in  Germany  as  here  in  America,  namely,  ball-mills,  Kominor,  tube, 
Griffin,  and  Fuller  mills. 

The  Portland  Cement  Works,  Heidelberg,  have  nothing  but 
Griffin  mills  running  in  six  of  their  seven  factories,  on  both  raw  ma- 
terial and  cement.  They  are  extremely  well  satisfied  with  them, 
and  get  a  larger  output  with  them  than  the  Americans.  However, 
some  improvements  have  been  made  on  the  mills.  Recently  two 
large  Fuller  mills  were  started  running  at  Heidelberg;  the  trials  with 
them  have  not  yet  been  concluded.  In  Germany  the  Kominor  with 
the  tube  mill  is  most  met  with,  though  this  does  not  by  any  means 
prove  that  this  system  of  grinding  is  especially  economical.  But, 
on  the  other  hand,  the  ball  and  tube  mill  is  a  very  reliable  method  of 
grinding,  and  it  requires  little  attention. 

It  will  interest  you  to  know  that  in  Germany  experiments  have  also 
been  made  with  burning  the  material  before  grinding.  It  was  also  a 
success  when  the  raw  material  was  crushed  to  1-inch  lumps.  This  burnt 
raw  material  proved,  however,  very  difficult  to  grind.  The  output 
of  the  mills  was  reduced  by  one-half,  and  on  this  account  the  matter 
was  not  followed  up.  In  any  case  the  burning  of  the  raw  material 
is  nothing  new. 

On  the  other  hand,  I  have  seen  in  another  factory  the  very  soft 
and  wet  material — similar  10  that  in  Sandusky — being  dried  in  a 
rotary  drier  120  feet  long  and  6  feet  6  inches  in  diameter  and  slightly 
burnt  at  the  same  time.  In  front  of  the  furnace  there  is  a  special 
combustion  chamber.  The  firing  is  done  with  coal-dust.  This 
factory,  which  formerly  could  never  get  its  raw  material  dry,  is  now 
working  very  successfully. 

The  mixing  of  the  raw  material  in  most  factories  in  Germany 
differs  from  the  American  method.  The  arrangement  you  have  here 
in  many  places,  of  weighing  the  clay  and  the  lime  and  then  mixing 
it,  is  rarely  met  with  in  Germany. 

Most  works  are  able,  on  account  of  their  favorable  raw  material, 
to  make  approximately  the  correct  composition  and  mixing  in  the 
pit,  where  the  removing  of  the  raw  material  is  done  exactly  in  accor- 
dance with  the  instructions  of  the  chemist.  The  chemist  knows 
exactly  which  layers  contain  more  lime  and  which  contain  more  clay. 
In  accordance  therewith  he  has  the  proper  proportion  of  clay  and 
lime  sent  up.  In  the  German  works  the  chemist  takes  the  first  place, 
and  he  also  supervises  the  whole  of  the  machine  plant.  You  will 
therefore  mostly  find  at  the  head  of  the  cement  works  in  Germany  a 


so-called  technical  chemist,  who  has  a  few  assistants  at  his  disposal 
in  the  laboratory.  Every  two  hours  the  percentage  of  lime  in  the 
raw  material  is  determined  in  the  laboratory,  and  according  to 
whether  it  turns  out  high  or  low,  instructions  are  given  to  send  up 
more  clay  or  more  lime.  Frequently  it  is  not  necessary  to  make  any 
change  for  days  together,  as  the  lime  and  clay  strata  are  fairly  uni- 
form in  their  composition.  No  importance  is  attached  to  the  mixture 
being  absolutely  even  as  it  comes  from  the  quarry,  as  usually  the  real 
mixing  is  done  only  after  the  grinding  of  the  raw  material.  For 
this  purpose  there  are  large  mixing  silos,  which  hold  25,000  barrels 
and  which  are  filled  up  in  regular  layers  during  the  course  of  a  week, 
and  are  then  mixed  together  when  withdrawing  the  ground  material. 
The  ground  material  can  be  laid  in  horizontal  or  vertical  layers.  A 
small  example  will  best  illustrate  this. 

A  factory  has  to  adjust  its  mixture  to  from  76  to  77  per  cent, 
carbonate  of  lime.  The  ground  material  is  passed  for  seven  days 
into  the  same  bin,  and  care  is  taken  to  spread  the  ground  material 
in  uniform  layers  by  means  of  suitable  conveying  machinery. 

If  the  material  has  been  stowed  in  horizontal  layers,  the  different 
layers  fall  together  when  emptying  the  bin,  and  so  give  an  average  of 
76.6  per  cent,  carbonate  of  lime. 

With  vertical  layers  the  conveyor  is  placed  under  the  bin,  and  the 
material  is  allowed  to  run  regularly  into  it  from  each  layer  through 
special  openings,  and  by  this  means  an  average  of  all  the  different 
layers  is  obtained.  As  the  composition  of  each  layer  is  determined 
daily  in  the  laboratory,  a  calculation  can  be  made  in  advance  as  to 
what  the  average  of  the  seven  layers  will  be.  There  are  usually  two 
bins,  and  while  the  one  is  being  emptied  the  other  is  being  filled. 
The  great  advantage  of  this  mixing  plant  is  that  very  large  quantities 
are  mixed  together,  by  which  great  uniformity  is  obtained.  Besides, 
no  machinery  is  required  and  the  making  of  the  proper  mixture  is 
entirely  in  the  hands  of  the  chemist. 

In  Westphalia  the  raw  material  has  naturally  nearly  the  correct 
composition,  and  the  ground  material  is  only  once  more  passed 
through  a  mixing  machine. 

The  burning  of  the  cement  is  to-day  done  in  rotary  kilns  in  two- 
thirds  of  the  German  factories.  Vertical  kilns  and  Hoffmann  ring 
kilns  are  still  found,  but  only  in  places  where  wages  are  very  low.  As 
the  latter  do  not  come  into  question  in  America,  I  will  not  dwell 
upon  them.  Regarding  the  construction  of  the  rotary  kilns,  they 
differ  only  slightly  from  the  American  kilns.  The  first  kilns  were 

10 


built  81  feet  long  and  6  feet  diameter,  but  the  length  was  gradually 
increased  to  120  feet,  and  recently  kilns  have  been  erected  150  feet 
long.  These  are  the  longest  up  to  the  present.  People  in  Germany 
are  not  yet  quite  clear  as  to  whether  the  long  kilns  are  better,  espe- 
cially as  they  have  been  able  to  use  the  waste  heat  with  advantage 
for  other  purposes.  The  economy  of  a  kiln  and  not  the  output  turns 
the  scale  in  Germany,  and  people  would  sooner  put  up  two  kilns  of 
smaller  capacity,  if  the  burning  can  be  done  therewith  more  economic- 
ally than  with  one  large  kiln. 


Fig.  6.— Dreadnaught-Kiln;  240  feet  Long,  10.5  feet  Diameter. 


The  engineering  works,  it  is  true,  recommend  long  kilns,  250  feet 
feet  in  length  and  9  feet  in  diameter,  as  with  these  the  end  gases  have 
a  temperature  of  only  200°  centigrade,  and  the  heat  is  best  utilized  in 
these  long  kilns.  But  no  kiln  of  such  length  is  in  operation  in  Germany. 

In  Germany,  where,  as  you  know,  fuel  is  very  dear,  it  was 
sought  from  the  commencement  to  utilize  the  heat  as  much  as 
possible.  On  this  account  each  rotary  kiln  is  provided  with  a  cooler, 
in  which  the  clinker  is  cooled  by  drawing  air  through  it.  The  same  fan 
which  blows  the  coal-dust  into  the  kiln  draws  the  air  through  the 
cooler,  which  is  thus  heated  to  250°  centigrade.  Thus  the  fuel  is 
saved  which  would  be  required  to  heat  the  large  quantity  of  air 

n 


required  for  burning  to  300°  centigrade.  Many  works  also  use  this 
hot  air  to  dry  the  coal.  Coolers  with  a  double  casing  have  also  been 
constructed,  so  that  the  clinker,  after  having  passed  through  the  inner 
cylinder,  is  led  back  through  the  outer  cylinder,  and  so  perfectly 
cooled.  The  air,  which  in  this  case  is  forced  from  the  front  into  the 
cooler,  reaches  a  temperature  of  300°  centigrade. 

One  company  uses  water  very  successfully  for  cooling  the  cylinder, 
the  hot  water  being  utilized  for  feeding  the  boilers  and  for  the  bathing 
arrangements  of  the  workmen. 


Fig.  7. — Installation  of  Fourteen  Rotary  Kilns;  Largest  Installation  in  Germany, 
Producing  4500  Barrels  a  Day. 

The  waste  heat  is  utilized  in  three  ways — either  to  dry  the  raw 
material,  to  warm  the  air  for  the  kilns,  or  to  raise  steam  in  the 
boilers. 

When  drying  the  raw  material  with  the  waste  gases  from  the 
kilns,  the  difficulty  for  a  long  time  was  that  considerable  dust  and 
fine  material  went  out  of  the  chimney,  but  this  is  now  arrested  by 
water,  producing  mud  which  is  burnt  under  the  kilns. 

When  the  waste  gases  are  utilized  for  heating  the  air  of  com- 
bustion, there  are  built  behind  the  kilns  so-called  blast-heaters, 

12 


Fig.  8. — Rotary  Kiln  for  Thick  Slurry  in  the  Weisenau  Plant  near  Mainz,  Ger- 
many.    A  double  cooler  with  cooling  by  compressed  air  is  shown  below  kiln. 


Fig.  9. — Rotary  Kiln  Installation  for  Thick  Slurry  Process.     Kilns  150  feet  long, 
9  feet  diameter.     A  newly  patented  shaker  is  shown  at  the  end  of  the  kilns. 

13 


which  are  said  to  heat  the  air  to  600°  centigrade.  Many  attempts 
have  been  made  to  utilize  the  waste  gases  for  raising  steainy  but 
in  most  cases  without  success,  as  no  means  were  known  of  keeping 


Fig.  10  —Coal-feeder  and  Fan  for  Rotary  Kiln. 

the  dust  from  the  tubes  of  the  boilers.  However,  three  factories 
are  to-day  using  the  waste  gases  of  the  kilns  for  raising  steam.  Two 
of  these  factories  have  kilns  90  feet  long,  while  one  uses  kilns  120 


feet  long.  The  production  of  steam  even  with  the  120-foot  kiln  is 
satisfactory.  The  steam  raised  by  the  waste  heat  not  only  suffices 
to  drive  the  whole  of  the  rotary  kiln  plant  and  the  coal  mill,  but  also 
furnishes  the  power  for  the  larger  part  of  the  raw  mill.  However, 
special  devices  of  a  rather  simple  nature  must  be  used  to  keep  the 
dust  from  the  boilers. 

The  injection  of  the  coal  is  done  by  fans,  which,  as  I  have  already 
mentioned,  draw  the  air  from  the  coolers.  In  order  to  obtain  perfect 
and  uniform  combustion  the  coal-dust  is  fed  into  the  air-current  of 
the  fan  by  means  of  a  system  of  double  worms.  By  this  means  the 


Fig.  11. — Concrete  Lining  of  a  Kiln. 

same  effect  is  said  to  be  arrived  at  as  that  aimed  at  by  Dunn's  uni- 
form pulverized  fuel  feeder.  But  according  to  my  observations  the 
problem  appears  to  be  better  solved  by  Dunn's  apparatus. 

Compressed  air  is  not  used  in  Germany  for  injecting  the  coal-dust. 
Experiments  therewith  showed  no  benefit.  The  pipes  through  which 
the  coal  is  injected  are  generally  wider  than  here — usually  8  inches. 

The  clinkering  zone  is  13  to  16  feet  distant  from  the  head  of  the 
kiln. 

The  lining  of  the  kilns  is  done  either  with  adhesive  sandbricks, 
firebricks,  or  bricks  made  of  clinker  and  cement. 

Adhesive  sandbricks  are  useless  unless  a  crust  is  formed  in  the  kiln, 

15 


as  otherwise  the  hard  clinker  causes  heavy  wear.  But  if  a  protective 
layer  of  clinker  is  deposited,  then  they  are  the  cheapest  kiln  lining. 

In  some  factories  attempts  have  been  made  to  simply  line  the 
kilns  with  concrete  made  of  a  mixture  of  rotary  kiln  clinker  and 
cement.  It  has  been  found  that  the  concrete  in  the  kiln  will  last  a 
long  time  (one  year),  if  the  kiln  is  allowed  to  stand  a  few  days  after 
the  lining,  so  that  the  concrete  can  harden  properly. 

As  you  are  aware,  a  patent  has  been  taken  out  in  Germany  for  a 
so-called  widened  clinkering  zone.  According  to  this  patent,  the 
front  part  of  the  kiln,  in  which  the  clinkering  proper  takes  place, 


Fig.  12.— Burner-stand  with  Fans  and  Pipes. 


and  which  otherwise  was  only  6  feet  6  inches  in  diameter,  is  enlarged 
to  8  feet  2  inches  diameter.  It  is  asserted  that  by  this  the  output 
of  the  kiln  is  increased  and  the  coal  consumption  reduced.  It  is 
very  difficult  to  get  an  opinion  on  this  point  from  actual  experience. 
The  manager  of  a  factory  who  works  with  such  kilns  told  me  the  only 
advantage  he  saw  was  that  a  very  thick  crust  formed  in  the  widened 
part  and  protected  the  kiln-lining  very  well.  In  general,  the  ad- 
vantages of  the  widened  clinker  zone  are  not  yet  clear,  and  preference 
is  given  to  a  kiln  the  diameter  of  which  is  at  the  outset  made  wide 
enough  in  its  entire  length. 

16 


Whereas  formerly  the  opinion  prevailed  that  the  ground  raw 
material  should  be  moistened  before  being  ^ed  into  the  kiln,  many 
factories  have  found  out  a  device  to  burn  the  dry  material.  The 
material  falls  direct  from  the  conveyor  through  a  pipe  into  the  kiln. 
By  this  means  the  mixing  worm,  which  required  attention  and  much 
power,  is  no  longer  required,  fuel  is  saved,  and  the  output  of  the  kilns 
is  increased  by  being  fed  with  dry  material.  Rotary  kilns  without 
coolers  are  not  found  in  Germany,  and  vertical  coolers  are  also 
unknown. 


Fig.  13. — Cooler,  Weighing  Machine,  and  Shaking  Conveyor. 

The  cooling-cylinders  are  always  placed  under  the  kilns  and  above 
the  floor.  The  foundations  of  the  kilns  are  therefore  much  higher 
than  is  usually  the  case  in  America. 

The  lubrication  of  the  bearings  is  done  with  calypsol  grease. 
Some  works  have  central  lubrication,  by  which  eight  to  ten  bearings 
are  automatically  greased  by  a  grease  pump. 

In  general,  three  kilns  are  attended  to  by  one  burner.  Ordinary 
workmen  are  usually  trained  as  burners,  and  on  account  of  their  easy 
work  they  are  paid  comparatively  low  wages.  Most  works  train  two 

17 


or  three  times  more  men  as  burners  than  they  require,  and  set  them 
to  other  work. 

When  the  waste  heat  of  the  kilns  is  used  for  raising  steam  in  the 
boilers,  one  man  can  attend  to  six  boilers,  his  sole  duty  being  to  feed 
the  boilers  with  water. 

The  front  end  of  the  cooler  is  perforated  like  a  screen  to  sort  the 
clinker,  and  only  the  coarse  clinker  requires  to  be  crushed  for  the 
cement  mill.  In  front  of  each  cooler  an  automatic  weighing  machine 
is  placed,  which  also  makes  automatic  records,  so  as  to  afford  an  exact 
check  on  the  output  of  each  kiln.  The  coal-dust  for  each  kiln  is 
weighed  in  the  same  manner,  and  coal  consumption  and  output  are 
noted  hourly  on  a  special  board. 

We  now  have  in  Germany  a  drum  weighing  machine,  with  which 
everything  can  be  weighed — pulverized  coal,  cement,  and  hot  clinker. 
It  is  very  exact  and  reliable. 

As  regards  conveyors,  preference  is  given  in  Germany  to  the  belt 
conveyor  and  to  the  worm  or  spiral  conveyor.  For  hot  clinker  the 
so-called  shaking  conveyor  is  much  used,  and  it  has  proved  very 
satisfactory;  it  is  not  the  type  oscillating  on  wooden  spring  legs, 
however,  but  a  shaking  trough  running  on  small  wheels.  This  con- 
veyor can  transport  any  quantity,  even  up  slight  inclines.  I  know 
of  a  factory  which  formerly  took  the  clinker  away  in  tip-cars,  and 
now  saves  fifty  workmen  after  installation  of  a  shaking  conveyor. 

Some  large  works  have  so-called  clinker  stores,  where  the  clinker 
is  stored  and  allowed  to  season. 

The  clinker  is  raised  by  means  of  a  bucket  elevator  to  a  height  of 
about  33  feet,  and  then  distributed  over  the  store  by  means  of  a 
shaking  conveyor,  which  is  designed  to  drop  the  clinker  in  different 
places.  The  removing  of  the  clinker  from  the  store  to  the  cement 
mill  is  also  done  by  means  of  such  a  shaking  conveyor  placed  in  a 
channel  under  the  clinker  store  and  covered  with  boards.  When 
the  boards  are  taken  up  (which  one  man  can  do)  the  clinker  falls  from 
the  store  into  the  conveyor  and  is  carried  away. 

The  storing  and  seasoning  of  the  clinker  has  many  advantages. 
In  the  first  place,  the  clinker,  being  dry,  grinds  better,  and  the  large 
lumps  become  soft  through  storage  and  easily  break.  Further,  the 
storage  is  good  for  the  quality  of  the  cement,  and  greater  uniformity 
is  obtained  by  being  able  to  again  mix  the  burnt  product  of  several 
days  before  grinding. 

The  cement  mill  in  a  German  works  has  the  same  appearance  as 


18 


in  American  works.  Ball-mills,  Kominor,  tube-mills,  Fuller  mills, 
and  Griffin  mills  are  used. 

The  finished  ground  cement  is  stored  in  large  square  bins  of  25,000 
to  100,000  barrels.  Preference  is  given  to  the  largest  bins  possible. 
This  is  to  get,  when  withdrawing  the  cement,  as  large  a  quantity  as 
possible,  by  which  great  uniformity  is  obtained.  Round  concrete 
silos,  which  of  late  are  frequently  met  with  in  America,  are  seldom 
used  in  Germany.  On  the  other  hand,  a  large  stock  of  cement  ready 
packed  in  bags  is  kept,  the  bags  being  piled  twenty-five  high. 

The  piling  of  the  sacks  is  done  by  a  band  conveyor. 


Fig.  14. — "Solomill"  for  Cement  Grinding;  a  Combination  of  Ball-  and  Tube-mill. 

For  packing,  the  automatic  twin  scales,  system  iron-work  Ahle- 
feld,  are  much  used,  which  weigh  very  correctly.  Capacity,  1800 
bags  in  ten  hours. 

Last  year  I  heard  that  certain  American  cement  manufacturers 
who  had  visited  German  cement  works  expressed  astonishment  at 
the  primitive  way  in  which  the  cement  is  packed  and  loaded  in 
Germany.  I  presume  that  the  gentlemen  in  question  had  only  visited 
some  unimportant  cement  works. 

With  the  high  wages  of  $1.25  to  $1.50,  which  have  to  be  paid  in 
Germany  to  men  in  the  packing  house,  you  will  find  to-day  well 

19 


designed  plants  in  the  larger  cement  works.     I  will  give  you  a  de- 
tailed description  of  one. 

The  storage  house  is  built  so  that  thirty  railway  cars  go  direct  into 
the  middle  of  the  house  on  two  tracks  running  side  by  side.  The 
room  in  which  the  cement  is  packed  is  situated  on  the  second  floor 
directly  over  the  railway  cars.  The  cement  is  taken  from  the  bins 
by  elevators  and  conveyors  to  the  thirty  automatic  packing  machines 
on  the  second  floor,  where  it  is  put  into  bags.  The  workmen  who 
fill  and  tie  the  bags  simply  let  them  slide  from  the  second  floor  down 
curved  tubes,  which  may  be  turned  around,  and  which  lead  into  the 
opened  railway  wagon.  In  each  case  there  is  a  man  who  takes  the 


Fig.  15. — Clinker  Store-house  with  Shaking  Conveyor. 

bag  from  the  tube  and  drops  it  into  its  place.  The  packers  on  the 
second  floor  fill  the  bags  as  quickly  as  the  man  down  in  the  wagon 
can  stow  them. 

In  other  works  where  the  railway  siding  is  a  long  way  distant 
from  the  packing  shed,  a  belt  conveyor  leads  from  the  packing  shed 
to  the  railway  cars,  and  the  bags  slide  down  an  inclined  chute  directly 
into  the  car,  where  they  are  stowed  by  one  man.  The  belt  conveyor 
runs  directly  in  front  of  the  packing  machines  on  a  level  with  the 
floor,  so  that  the  workmen  can  lay  the  bag  directly  on  the  conveyor 
as  soon  as  it  is  filled  and  tied  up.  If  six  automatic  scales  are  at  work, 

20 


the  bags  follow  one  another  on  the  belt  conveyor  at  intervals  of 
feet,  and  a  car  can  be  filled  in  ten  minutes,  though  I  should  here 
remark  that  the  German  railway  cars  do  not  hold  more  than  300  bags. 

A  special  arrangement  for  packing  cement,  invented  and  intro- 
duced by  the  firm  of  Smith  &  Co.,  has  been  running  in  some  works 
for  about  a  year.  The  cement  is  put  into  the  bags  by  vacuum. 

Gentlemen,  you  are  aware  that  Germany  exports  one-tenth  of 
its  production.  Exports  are  chiefly  from  the  factories  which  lie 
on  the  coast  and  the  big  rivers.  As  cement  is  only  exported  in 
barrels,  all  these  works  have  a  special  cooperage  and  packing  plant 
for  barrels.  In  order  that  the  barrels  may  withstand  a  long  oversea 
voyage,  the  cement  must  be  tightly  pressed.  In  most  factories  the 
packing  of  these  barrels  is  done  by  hand,  the  filled  barrels  being  well 
beaten  with  clubs  until  the  cement  has  thoroughly  settled.  But 
there  are  also  machines  for  this  work.  The  barrel  stands  on  a 
revolving  plate  and  is  kept  rotating  while  receiving  a  number  of 
powerful  shakes  from  a  mechanical  device.  In  order  to  render  them 
perfectly  water-tight,  the  barrels  are  lined  with  water-tight  paper. 

The  making  of  these  barrels  forms  a  special  department,  which, 
on  account  of  its  liability  to  catch  fire,  is  usually  in  a  building 
separated  from  the  other  buildings.  In  Heidelberg,  for  instance,  over 
a  hundred  workpeople  are  employed  in  this  department.  With 
the  exception  of  the  putting  on  of  the  wooden  hoops  and  the  fitting 
of  the  lids,  the  barrels  are  all  made  by  machinery.  The  large  works 
have  their  own  saw  mills,  where  the  wood,  as  it  comes  from  the  forests, 
is  sawn  into  cylindrical  staffs,  grooved,  molded,  and  fitted  together 
by  special  machinery.  The  making  and  putting  on  of  iron  hoops  is 
also  done  by  machinery. 

Bags  made  of  jute  are  mostly  used,  rarely  of  canvas.  Paper  bags 
are  still  too  dear  in  Germany  and  therefore  not  used.  The  cleaning 
of  the  bags  is  done  in  the  same  way  as  in  America,  namely,  in  large 
revolving  drums.  Electric  sewing  machines,  with  dust  exhausters, 
are  used  for  sewing  and  mending.  It  will  interest  you  to  know  that 
a  group  of  twenty  cement  works  in  Westphalia  have  a  so-called  "bag 
central,"  where  new  bags  are  made  and  the  old  ones  cleaned  and 
repaired.  The  empty  bags  are  sent  by  the  customers  to  the  "cen- 
tral," where  they  are  sorted,  repaired,  cleaned,  and  returned  to  the 
different  works. 

The  cost  of  the  whole  work  does  not  amount  to  quite  half  a  cent 
per  bag.  Only  women  are  employed  for  mending. 

The  same  group  has  also  its  own  barrel  factory,  in  which  the  bar- 

21 


rels  for  about  twenty  works  are  made.     This,  of  course,  can  be  done 
only  when  the  works  are  close  together. 

As  the  German  cement  works  are  mostly  somewhat  old,  you  will 
find  in  them,  in  contrast  to  American  factories,  long,  complicated 
line-shafting,  from  which  the  mills  are  driven.  Compared  with 
America,  the  motor  drive  is  much  rarer,  but  it  is  gradually  being 
introduced,  especially  in  the  more  recent  works.  The  firm  of  Dycker- 


Fig.  16.— The  Music  Hall  under  Con- 
struction. 


Fig.  17.— The  Music  Hall  Inside  with 
the  Stage. 


Fig.  18. — Swimming  Bath  for  the  Laborers. 


hoff  has  installed  in  its  new  works  steam-turbines,  and  for  driving  the 
grinding  machinery  nothing  but  motors. 

For  raising  steam  you  will  find  all  boiler  and  stoking  systems 
represented.  The  stoking  is  mostly  automatic. 

The  Leimen  factory  has  a  swimming  bath  100  feet  long  by  50  feet 
wide  for  the  workpeople.  Slipper-baths  and  shower-baths  are  con- 
nected with  it.  The  picture  shows  you  that  it  has  been  fitted  up 

22 


rather  luxuriously  in  order  to  encourage  the  workpeople  to  make  use 
of  it. 

The  same  works  built  a  music  hall  two  years  ago  for  the  workmen, 
in  which  they  hold  their  festivities  every  week.  Connected  with  it 
there  is  a  " kindergarten,"  a  library,  and  a  reading-room. 

Gentlemen,  the  same  as  here  in  America,  many  factories  have 
built  houses  in  the  neighborhood  of  the  works,  in  which  the  work- 
people can  live  at  a  low  rent.  Recognizing  that  it  is  a  great  ad- 
vantage for  a  factory  to  have  old,  well-trained  workmen,  they 
are  given  every  consideration.  Almost  every  factory  has  its  own 


Fig.   19. — Cement  Factories  in  Leimen  near  Heidelberg.     In  the  foreground  is 
shown  a  Music  Hall  and  Houses  for  the  Laborers. 


sick  fund,  saving  club,  pension  fund,  eating  houses,  and  canteen. 
It  is  nothing  unusual  for  workmen  to  remain  twenty-five  to  forty 
years  in  one  factory.  Following  the  example  set  by  America,  almost 
every  factory  has  its  own  repair  shop,  and  at  the  Portland  Cement 
Works  of  Heidelberg  and  Mannheim,  for  instance,  the  repair  shop  is 
as  large  as  an  engineering  works.  Not  only  are  all  repairs  and 
improvements  on  mills  and  machinery  made  there,  but  the  works 
have  their  own  foundry,  to  which  a  steel  foundry  is  now  being  added. 
New  machinery  is  also  made  there;  it  is  a  sort  of  experiment  station 
for  new  ideas. 

23 


As  far  as  I  can  judge,  the  cost  of  production  is  lower  in  Germany 
than  in  America,  and  for  this  the  lower  wages  are  not  alone  respon- 
sible. To  counterbalance  this,  fuel  is  dearer  in  Germany.  But  the 
German  does  more  calculating;  he  tries  to  save  every  cent,  and  makes 
full  use  of  every  advantage,  as,  for  example,  the  temperature  of  the 
waste  gases,  new  conveyors,  etc.  But  what  gives  a  special  advantage 
to  the  different  works  are  the  monthly  actual  cost  calculations,  which 
show  clearly  and  to  the  smallest  detail  how  high  the  actual  cost  is 
in  every  single  branch.  The  art  of  correctly  calculating  the  actual 
costs,  of  studying  the  same,  and  drawing  from  them  the  proper  con- 
clusions as  to  where  the  lever  should  be  applied  to  lower  the  cost  of 
production,  this  art  enables  many  factories  to  manufacture  much 
cheaper  than  others,  who  otherwise  are  just  as  favorably  placed. 

A  well-managed  works  sees  from  this  statement  of  actual  costs 
where  faults  are  to  be  corrected,  and  is  urged  by  it  to  make  the  cost 
still  cheaper  in  the  following  month  by  the  application  of  improve- 
ments and  by  making  use  of  certain  advantages.  And  in  this  manner 
people  have  managed  in  Germany  continually  to  reduce  the  actual 
cost  of  a  barrel  of  cement,  in  spite  of  higher  wages  and  dearer  fuel. 
A  limit  will  no  doubt  be  reached  in  time,  but  from  what  I  have  seen 
my  conviction  is  that  in  America  you  are  much  further  from  this 
limit  than  in  Germany.  The  Germans  have  taken  lessons  from  the 
Americans  with  regard  to  their  kilns  and  grinding  machinery;  let 
the  Americans  learn  from  the  Germans  how  to  make  use  of  everything 
in  order  to  save  every  cent  and  make  cement  as  cheap  as  possible. 

I  cannot  predict  offhand  which  will  eventually  prove  to  be  more 
advantageous  for  America,  the  wet  process  with  thick  slurry  or  the 
dry  process.  But  it  is  possible  that  in  America  the  wet  process  may 
prove  cheaper,  because  fuel  is  considerably  cheaper  than  in  Ger- 
many, and  therefore  the  cost  of  burning  the  cement,  which  in  any 
case  is  higher  with  the  wet  process  than  with  the  dry,  may  not  be 
of  so  great  account. 

As  I  am  aware  that  the  American  cement  industry  is  greatly 
interested  in  the  wet  process,  I  will  say  a  few  words  about  it  at  the 
close  of  my  lecture. 

Many  of  the  works  situated  in  the  north  of  Germany  make  their 
cement  from  the  chalk  on  the  coast  and  on  the  Baltic  islands,  and 
are  forced  to  use  at  the  same  time  a  clay  containing  much  sand 
and  flint,  and  they  have,  like  most  of  the  works  in  England, 
always  given  preference  to  the  wet  process.  Chalk  and  clay  contain 
naturally  a  high  proportion  of  moisture,  and  are  also  so  soft  that  they 

24 


can  be  reduced  to  the  requisite  fineness  without  mills,  simply  by  wash- 
ing. In  these  factories  the  raw  materials  are  washed  very  thin  with 
about  80  per  cent,  of  water,  and,  according  to  the  arrangement  of 
the  plant,  the  stones  and  the  coarse  sand  either  settle  to  the  bottom 
as  the  heavier  constituents,  or  they  are  separated  from  the  thin 
slurry  by  screens.  The  slurry  runs  from  the  washing  basins  into  large 
settling  basins,  where  it  is  allowed  to  settle.  The  water  collecting 
on  top  is  let  off  from  time  to  time,  and  the  sun  and  air  help  gradually 
to  dry  out  the  water  remaining  in  the  slurry  until  it  becomes  stiff 
enough  to  be  dug  out  with  a  spade  and  pressed  into  bricks  for  the 
shaft  or  ring  kilns,  which  are  still  used  by  most  of  the  factories  that 
work  on  the  wet  process.  Some  of  these  factories,  however,  have 
recently  installed  rotary  kilns,  and  pump  the  slurry  containing  40  to 
55  per  cent,  water  direct  from  the  settling  basins  into  the  kilns.  It 
is  often  months  before  the  slurry  gets  the  consistency  desired,  and 
it  is  certainly  a  disadvantage  of  this  wet  process  that  so  much  time 
is  lost  before  the  product  made  months  ahead  can  be  actually  turned 
to  value.  Enormous  values  are  often  represented  by  this  half- 
finished  product. 

The  wet  process  is  considerably  more  advantageous,  when  pure 
chalk  and  clay  are  to  be  had,  and  it  is  not  necessary  to  pay  attention 
to  eliminating  impurities  in  the  shape  of  quartz  sand  and  flint. 
The  addition  of  40  per  cent,  water  then  suffices  to  grind  the  material 
in  the  wash-mills.  This  slurry  is  then  simply  run  into  the  so-called 
mixing  basins,  where  it  is  stirred  up  until  the  mixture  is  uniform. 
It  is  not  necessary  to  thicken  further  this  40  per  cent,  slurry,  and 
it  can  be  pumped  direct  to  the  kilns. 

With  these  two  ways  of  wet  preparation  it  is  presumed  that  the 
chalk  and  clay  are  naturally  so  soft  that  no  special  mills  are  necessary 
for  grinding. 

But  it  should  especially  interest  you  in  America  that  recently 
some  works  have  started  to  prepare  hard  materials  like  limestone 
in  the  wet  way  by  using  special  mills.  This  so-called  thick  slurry 
process  has  so  far  been  introduced  in  Germany  into  seven  factories, 
of  which  I  inspected  five  during  my  last  stay  in  Germany. 

Before  I  give  you  a  full  explanation  of  why,  according  to  the  opin- 
ion at  present  prevailing  in  Germany,  thick  slurry  preparation  is  to 
be  preferred  to  dry  preparation,  I  should  like  to  give  you  a  short 
description  of  the  working  of  a  thick  slurry  plant. 

Such  a  plant  is  mostly  built  in  four  stories,  one  above  the  other. 

The  material   comes  from  the  pit  to  the  top  floor.     The  large 

25 


pieces  of  limestone  are  here  crushed  to  the  size  of  a  fist  and  fall  directly 
onto  the  wet-kominors  placed  below.  The  soft  wet  clay  and  marl 
are  fed  directly  into  this  wet-kominor,  and  roughly  ground  with  the 
addition  of  water.  The  rough  slurry,  which  has  35  to  45  per  cent, 
moisture,  runs  into  the  wet  tube-mills,  which  are  placed  in  the  floor 
below  under  the  wet-kominors,  and  here  it  is  ground  quite  fine.  The 
factory  has,  according  to  its  size,  a  number  of  large  mixing  basins, 
which  lie  below  and  in  front  of  the  wet  tube-mills,  and  the  slurry 
runs  through  pipes  into  these  basins.  A  factory  producing  1000 


G.Potysii 


Fig.  20. — Triple  Mixer  with  Practicable  Gangway  all  Round. 

barrels  daily  requires  at  least  four  mixing  basins  of  500  barrels  capacity 
each.  As  soon  as  a  basin  is  three-quarters  full,  the  mixture  is  made 
by  testing  the  slurry  every  two  hours  and  then  grinding  material 
either  richer  in  clay  or  richer  in  lime  and  allowing  it  to  run  into  the 
basin.  The  final  adjustment  can  also  be  done  by  letting  the  slurry 
run  from  one  basin  into  the  other.  The  mixing  basins  are  usually 
oval  in  shape;  three  stirrers  run  in  each  basin  to  keep  the  slurry 
in  constant  motion  and  mix  it. 

The  slurry  is  then  pumped  by  means  of  special  pumps  to  small 
slurry  bins  over  the  kilns,  and  is  burnt  in  the  rotary  kiln  in  exactly 

26 


the  same  manner  as  dry  material.  The  feed  pipe  to  the  kiln  must 
be  steep  and  wide,  so  that  it  does  not  choke.  A  difficulty  with  the 
burning  is  that  the  slurry  is  apt  to  roll  together  into  large  balls,  which 
pass  through  the  clinkering  zone  too  quickly  and  do  not  get  thoroughly 
burnt  inside.  These  are  called  " runaways." 

The  kilns  for  the  thick  slurry  process  have  in  Germany  generally 
a  length  of  122  to  148  feet,  and  are  7  feet  6  inches  to  8  feet  2  inches 
diameter.  Only  the  kilns  in  the  Dyckerhoff  works  are  longer — 150 
feet  long  and  9  feet  in  diameter.  Otherwise  they  are  exactly  the 


G.Potysms,  Dessau. 

30/17. 


Fig.  21.— Slurry  Storage  and  Mixing  Tanks,  with  Feeders,  and  Slurry  Worm 
Conveyor  above  the  Rotary  Kilns. 


same  as  kilns  for  the  dry  process.  The  clinker  is  just  as  hard  as 
the  clinker  made  from  dry  material,  and  there  is  no  difference  in 
the  further  process  of  manufacture.  Last  year  I  often  heard  the 
view  expressed  here  in  America  that  people  in  Germany  were 
going  over  to  the  thick  slurry  process  quite  generally.  This  is  a 
mistake.  As  I  have  already  told  you,  there  are  at  the  present  time 
in  Germany  only  seven  such  works,  and  with  all  of  these  special 
reasons  led  to  the  introduction  of  the  thick  slurry  process.  Two  of 
these  works  used  the  wet  process  from  the  beginning.  At  the  moment 

27 


only  a  single  factory  is  altering  its  plant  to  the  wet  process,  and 
from  this  you  may  see  that  the  majority  of  the  German  cement  makers 
still  consider  the  dry  process  better,  and  in  any  case  more  econom- 
ical. Only  very  special  reasons,  such  as  peculiarities  of  location 
or  a  naturally  very  wet  raw  material  that  could  not  be  dried, 
have  induced  the  German  cement  maker  to  introduce  the  thick 
slurry  process  in  a  few  places,  although  three  engineering  works 
are  already  making  wet  mills,  and  on  this  account  are,  of  course, 
advocating  the  wet  process.  The  best  German  cements  with  the 
highest  degrees  of  strength  are  still  the  cements  made  with  the  dry 
process,  so  the  question  of  quality  is  no  inducement  to  go  over  to  the 
wet  process.  With  proper  attention  just  as  good  cement  can  be 
made  in  the  dry  way  as  in  the  wet,  if  the  correct  arrangements  are 
made  for  a  thorough  mixing.  Still  there  may  be  instances  where 
the  wet  process  is  to  be  preferred  to  the  dry,  but  such  cases  can  only 
be  decided  separately  after  a  thorough  testing  of  the  raw  material. 
I  will  give  you  the  points  of  view  to  be  considered  before  deciding, 
especially  in  Germany,  where  fuel  is  very  dear  and  forms  a  consider- 
able part  of  the  cost  of  manufacturing.  In  this  respect  the  position 
in  America  may  differ  somewhat,  as  you  have  cheap  coal  and  oil  at 
your  disposal  for  burning  the  cement.  But  if  you  can  save  only  a 
few  cents  a  barrel  with  the  dry  process  compared  with  the  wet  process, 
then  here,  too,  you  must  give  the  preference  to  the  dry  process  of 
making  cement. 

The  economy  in  burning  cement  in  rotary  kilns  depends  on  the 
following  four  points:  (1)  Cost  of  the  installation;  (2)  wages;  (3) 
power  consumption;  (4)  coal  consumption. 

The  cost  of  plant  is  undoubtedly  lower  for  the  wet  process,  as 
various  arrangements  are  not  required  which  are  necessary  for  the 
dry  process.  No  rotary  driers  are  required  nor  bins  for  ground  raw 
material,  the  latter  being  substituted  by  the  cheaper  mixing  basins. 
There  is  not  required  for  the  wet  process  the  dust-collecting  ar- 
rangements for  the  raw  mill.  The  buildings  for  the  dry  process  also 
take  up  rather  more  room.  The  opinion  that  with  the  wet  process 
the  kilns  would  have  to  be  longer  and  larger  has  proved  wrong,  so  that 
with  the  dry  process  the  same  cost  of  installation  has  to  be  taken 
into  account  for  the  kilns  as  with  the  wet  process.  However,  the 
extra  cost  of  a  dry  plant  compared  with  a  wet  plant  is  not  as  much 
as  might  be  assumed  from  the  foregoing.  It  amounts  to  3  to  5  per 
cent,  on  the  complete  plant,  and  plays  no  great  part  when  calculated 
on  the  barrel.  f/- 


In  America  an  important  consideration  is  whether  the  wet  pro- 
cess will  reduce  labor  costs.  According  to  the  experience  in  Germany, 
this  is  not  the  case.  As  many  people  are  required  for  attending 
to  the  wet  grinding  machines  and  the  mixing  basins  as  with  the 
dry  process  for  attending  to  the  mills  and  ground  material  bins. 
The  power  consumption  of  the  mills  is  generally  lower  with  the  wet 
process,  especially  with  materials  which  are  not  of  a  hard  nature, 
such  as  marl,  clay,  chalk,  etc.  With  such  stuff  the  washing  with 
water  is  effective  and  divides  the  material  into  its  finest  parts,  so 
that  the  mills  have  little  work  to  do.  But  it  is  a  different  thing 
if  hard  limestone  and  shale  are  to  be  ground  wet,  as  the  water  is 
then  of  no  assistance,  and  the  mills  have  to  do  the  same  work  as 
with  the  dry  process.  The  economy  in  power  is  then  very  low  and 
out  of  proportion  to  the  higher  coal  consumption  necessary  to  evapo- 
rate in  the  kiln  the  added  water;  and  the  higher  the  proportion  of 
water  in  the  slurry,  the  higher  the  coal  consumption  naturally  is. 

In  judging  the  relative  economy  of  the  two  systems,  the  main 
question  is  the  coal  consumption.  Because,  as  the  situation  lies  in 
Germany,  coal  is  the  chief  factor  in  the  actual  cost  of  manufacture, 
amounting  from  one-third  to  one-half  of  same,  according  to  price 
and  other  circumstances.  Thus  when  making  cement  consideration 
must  be  given  in  the  first  place  to  saving  coal. 

Most  of  the  factories  with  the  thick  slurry  process  work  with  a 
40  per  cent,  proportion  of  water.  It  depends  on  the  nature  of  the 
raw  material  whether  more  or  less  water  must  be  added.  Occasion- 
ally slurry  with  45  per  cent,  water  is  still  so  stiff  that  it  can  hardly 
be  pumped.  There  are  works  which  burn  even  55  per  cent,  slurry 
in  the  rotary  kilns. 

With  55  per  cent,  water  there  has  to  be  evaporated  190  parts  of 
water  to  100  parts  of  finished  cement,  which  is  a  very  unfavorable 
ratio.  With  a  thick  slurry  containing  40  per  cent,  water  the  ratio 
is  much  better,  but  104  parts  of  water  have  still  to  be  evaporated 
to  100  parts  of  cement.  It  is  clear  that  an  increased  expenditure  of 
coal  is  necessary  to  burn  cement  out  of  a  material  containing  so  much 
water.  Experience  has  shown  that  with  the  kilns  mostly  used  in 
Germany,  115  to  148  feet  long  and  7  feet  2  inches  to  8  feet  2  inches 
in  diameter,  the  burning  of  a  slurry  containing  35  to  40  per  cent, 
moisture  requires  in  round  figures  for  every  100  kilos  of  cement  5 
kilos  more  coal  of  medium  quality  than  the  burning  of  a  slightly 
damped  ground  raw  material,  including  the  preliminary  drying  of 
material  from  the  quarry  with  the  average  moisture  in  the  pit. 

29  ' 


The  bill  for  fuel  is  therefore  increased  by  fully  20  per  cent,  with 
the  wet  process. 

These  figures  thus  result  from  the  comparison  of  the  burning  of 
thick  slurry  and  dry  raw  material  in  kilns  of  the  same  length  and 
diameter,  and  after  taking  into  account  the  amount  of  coal  required 
by  the  dry  process  for  drying  the  raw  material  before  grinding. 
Besides  this,  the  dry  ground  raw  material  was  moistened  with  8  to 
10  per  cent,  water  before  burning.  All  these  are  very  unfavorable 
conditions  for  the  dry  process.  In  a  properly  managed  kiln  plant 
with  the  dry  process  the  result  will  turn  out  much  more  unfavorable 
to  the  wet  process  than  I  have  shown  to  you. 

In  the  first  place,  it  is  not  necessary  to  damp  the  raw  meal  with 
8  to  10  per  cent,  water  when  running  it  into  the  kiln.  Some  factories 
have  long  had  a  device  which  renders  it  possible  to  burn  directly 
the  dry  meal,  so  that  the  fuel  for  evaporating  this  8  to  10  per  cent, 
water  can  also  be  saved.  There  has  also  btei  left  out  of  considera- 
tion the  fact  that  with  kilns  115  to  148  feet  in  length  the  waste 
heat  when  burning  thick  slurry  only  amounts  to  250°  centigrade, 
whereas  with  the  dry  process  the  waste  heat  has  a  temperature  of 
500°  centigrade  and  over.  As  I  have  previously  explained  to  you, 
this  waste  heat  can  be  utilized  for  warming  up  the  air  of  combustion 
in  blast-heaters,  or,  better  still,  for  raising  steam  in  the  boilers. 
On  the  other  hand,  when  burning  thick  slurry  the  heat  produced  by 
the  fuel  is  all  used  up  in  evaporating  the  water,  so  that  the  waste 
gases  have  a  temperature  of  only  250°  centigrade,  and  cannot  be 
further  utilized. 

But  it  is  precisely  the  utilization  of  the  waste  heat  that  enables 
further  economies  to  be  made,  which  I  estimate  very  high  if  properly 
planned.  The  firm  of  Polysius,  in  Germany,  which,  as  the  first  fac- 
tory for  the  construction  of  rotary  kilns,  has  much  experience  in 
this  line,  explained  a  year  ago,  through  their  Director  Bruhn,  the 
advantages  of  the  dry  process  in  a  lecture  given  at  the  meeting  of 
the  German  Portland  Cement  Makers,  and  the  theories  set  forth 
coincide  exactly  with  the  statements  made  by  me  to-day.  Dr. 
Bruhn  also  comes  to  the  conclusion  that  the  dry  process  is  to  be  pre- 
ferred to  the  wet  process,  unless  the  raw  material  has  naturally  more 
than  15  per  cent,  moisture  and  by  its  softness  is  specially  suitable 
for  wet  grinding  and  washing.  This  firm  builds  at  the  same  time 
wet  mills  and  kilns  for  thick  slurry. 

But  Dr.  Bruhn  is  not  of  my  opinion  that  it  is  best  to  utilize  the 
waste  heat  for  the  driers  or  boilers,  as  this  makes  the  plant  compli- 

30 


cated,  and  he  recommends  building  the  kilns  of  such  a  length  that 
all  the  heat  is  thoroughly  utilized  in  the  kiln  itself  in  burning  the 
raw  meal,  so  that  the  waste  gases  have  a  temperature  of  only  250° 
centigrade.  It  was  ascertained  by  experiments  that  to  fulfil  these 
conditions  a  kiln  must  have  a  length  of  262  feet  by  8  feet  2  inches 
diameter. 

When  the  firm  of  Polysius  now  builds  new  works,  it  seeks  to 
introduce  these  long  kilns,  which  are  said  to  reduce  the  coal  con- 
sumption and  to  increase  the  output  of  the  kiln. 

However,  the  wet  preparation  has  in  any  case  several  advan- 
tages, the  principal  of  which  is  that  the  plant  is  much  simpler  with 
wet  grinding,  and  the  adjustment  of  the  proper  mixture  is  easier 
with  thick  slurry  than  with  raw  meal.  Any  mistakes  can  be  cor- 
rected without  difficulty  in  the  mixing  basins.  But  I  do  not  mean 
to  say  that  on  this  account  the  quality  of  cement  burnt  from  thick 
slurry  is  better  than  that  made  from  raw  meal.  With  the  employ- 
ment of  proper  mixing  arrangements  and  with  care  the  same  uni- 
formity and  accuracy  in  the  composition  of  the  raw  meal  can  be  at- 
tained with  the  dry  process.  When  this  is  not  the  case,  it  is  not  the 
method  but  the  arrangements  that  are  at  fault. 

The  disadvantage  of  the  thick  slurry  process  is  thus  undoubtedly 
in  the  extra  expenditure  in  fuel  and  the  increased  cost  of  manufacture 
caused  thereby,  which  will  become  the  more  palpable  in  comparison 
with  the  dry  process  when  the  burning  of  dry  meal  and  the  utilization 
of  the  waste  heat  are  properly  understood. 

On  the  other  hand,  the  thick  slurry  plant  has  some  advantages 
which  may  be  briefly  stated  as  follows :  (1)  Smaller  capital  investment 
in  the  installation.  (2)  Little  dust.  (3)  The  possibility  of  proper 
adjustment  of  the  mixture  without  difficulty.  (4)  A  simpler  plant 
and  fewer  conveyors.  (5)  Saving  of  power  in  wet  grinding. 

The  saving  in  power  is  very  small,  however,  and  is  not  nearly  com- 
pensated for  by  the  larger  expenditure  in  coal  required  for  the  burning 
of  the  thick  slurry,  and  it  would  not  be  right,  therefore,  to  give  the 
wet  process  the  preference  over  the  dry  on  account  of  the  saving 
in  power.  Dr.  Bruhn  gave  in  his  lecture  last  year  the  following 
explanations,  which  will  show  you  the  position  clearly:  "With  our 
steam-engines  of  to-day  0.7  kilo  of  medium  quality  coal  is  sufficient 
to  produce  1  horse-power-hour.  With  kilns  of  equal  length,  5  kilos 
less  coal  per  100  kilos  clinker  are  used  when  burning  raw  meal  than 
when  burning  slurry  containing  35  to  40  per  cent,  water.  These 
5  kilos  of  coal  are  thus  equal  to  7  HP-hours.  With  a  production  of 


10,000  kilos  per  hour,  equal  to  300,000  barrels  per  year,  this  higher 
consumption  of  fuel  in  the  thick  slurry  kiln  is  equivalent  to  a  constant 
higher  expenditure  of  700  PS  per  hour.  But  the  whole  plant  for 
this  production  only  requires  some  300  to  400  HP  for  crushing,  drying, 
and  grinding  the  raw  meal." 

Gentlemen,  I  can  only  confirm  this  from  the  experience  made 
by  a  company  to  which  I  formerly  belonged,  and  which  altered  one 
of  its  works  to  the  thick  slurry  system.  The  factory  in  question 
works  at  much  greater  cost  than  the  other  factories  with  the  dry 
process. 

It  is  very  difficult  to  give  a  general  opinion  as  to  whether  the 
dry  process  or  the  wet  process  is  more  advantageous.  Where  err- 
phasis  is  placed  on  having  a  plant  as  simple  as  possible,  and  that 
can  be  easily  supervised,  or  where  there  are  difficulties  in  attaining 
a  good  mixing  with  the  dry  method,  in  such  cases  the  wet  process 
is  perhaps  suitable,  even  if  the  raw  material  is  naturally  hard  and 
not  too  damp.  But  in  any  case  it  must  be  taken  into  account  that 
the  cost  of  manufacture  will  be  considerably  higher  than  if  the  same 
material  were  worked  dry.  The  method  of  making  is  certainly  simple 
and  easy,  but  it  costs  more. 

It  is  somewhat  different  if  the  materials  are  naturally  soft  or 
impure  and  contain  much  moisture,  so  as  to  render  the  drying  difficult. 
In  such  a  case  the  wet  process  would  be  preferable.  As  far  as  I  had 
the  opportunity  of  examining  the  raw  materials  used  in  America  for 
making  cement,  I  am  convinced  that  most  of  them  are  more  suitable 
for  the  dry  process  than  for  the  wet  process. 

I  have  already  mentioned  that  a  cement  works  in  Germany  is 
now  about  to  change  from  the  dry  process  to  the  wet;  the  reasons 
are  that  the  factory  in  question  has  to  work  a  clay  containing  15 
per  cent,  moisture,  and  adds  12  per  cent,  water  to  the  raw  meal  before 
it  runs  into  the  kiln.  Under  such  circumstances  the  superintendent 
said  that  it  did  not  matter  so  much  whether  he  added  a  further  10 
per  cent,  water  and  introduced  the  thick  slurry  system,  especially 
as  he  was  never  able  to  dry  the  clay  properly.  But  I  know  of  another 
works  which  is  at  present  making  alterations,  but  is  retaining  the 
dry  system,  although  the  clay  contains  nearly  20  per  cent,  water. 
The  works  in  question  has  constructed  for  itself  a  special  cylinder 
drier  with  coal-dust  firing,  and  as  they  know  how  to  burn  the  raw 
meal  dry,  I  do  not  doubt  that  this  factory  will  manufacture  cheaper 
than  the  other  factory  with  the  thick  slurry  system.  You  see, 
gentlemen,  that  also  in  Germany  the  question  as  to  whether  the  wet 

32 


or  dry  process  is  better  has  not  been  sufficiently  cleared  up.  My 
personal  view  is  that  wet  preparation  should  only  be  chosen  if  the 
raw  materials  are  not  hard  or  plastic,  and  if  the  natural  proportion 
of  moisture  already  approaches  that  necessary  for  wet  working.  I 
consider  it  a  mistake  to  work  hard,  dry  material  according  to  the 
wet  process  simply  for  the  purpose  of  facilitating  the  mixing  or  of 
avoiding  the  dust.  For  to  solve  both  these  problems  it  is  not  neces- 
sary to  introduce  the  more  expensive  wet  process;  it  can  be  done 
just  as  well  with  the  dry  process. 

I  hear  that  a  factory  is  being  changed  in  America  to  the  wet 
system,  and  it  will  then  be  seen  whether  the  wet  system  is  pref- 
erable for  your  country,  which  is  not  impossible,  as  fuel  does  not 
play  such  a  large  part  in  the  cost  of  manufacturing  as  with  us  in 
Germany. 


The  Laboratory  of  the  Association  of  Ger- 
man Cement  Makers  and  the  New 
German  Rules  for  the  Uniform  Test- 
ing and  Delivery  of  Portland  Cement. 


BY  DR.  OTTO  SCHOTT 


When  in  the  year  1877  the  representatives  of  the  German  cement 
industry,  which  at  that  time  hardly  produced  two  and  one-half 
million  barrels,  joined  together  to  form  an  Association  of  German 
Cement  Makers,  this  association  set  itself  the  task  of  furthering  all 
interests  touching  the  Portland  cement  industry,  and  of  contributing 
by  scientific  work  to  the  knowledge  of  the  properties  of  Portland 
cement.  How  energetically  it  went  to  work  is  probably  best  seen 
by  the  rules  it  laid  down  on  a  scientific  basis  in  the  same  year  for 
uniform  methods  of  testing  Portland  cement,  and  which  have  become 
a  pattern  for  the  cement  industry  of  the  whole  world,  although  they 
have  undergone  many  changes  in  the  course  of  time.  Notwithstand- 
ing that  Portland  cement  had  been  made  in  England  for  fifty  years, 
it  is  rather  remarkable  that  this  was  the  first  attempt,  with  the  help 
of  experience  and  researches  made  up  to  that  time,  to  lay  down 
uniform  methods  for  the  testing  of  Portland  cement.  This  meant 
immense  progress  for  the  cement  industry,  as  the  users  of  cement  were 
thereby  enabled  to  test  and  work  the  cement  in  a  proper  manner,  and 
to  judge  the  quality  correctly. 

The  laying  down  of  the  rules  had,  however,  a  further  advantage 
for  the  cement  makers  in  that  they  showed  that  much  was  still  to  be 
cleared  up  with  regard  to  the  properties  of  cement,  and  that  next 
to  nothing  was  known  regarding  the  constitution  and  cause  of  hard- 
ening of  Portland  cement,  so  that  the  impulse  was  given  to  study  these 
questions.  The  German  cement  makers  applied  themselves  with  much 
diligence  and  zeal  to  these  questions.  Many  works  appeared  which 
gave  explanations  regarding  the  properties  of  Portland  cement,  and  so 

34 


contributed  to  clear  up  the  questions  as  to  the  proper  way  of  making, 
testing,  and  treating  Portland  cement.  The  value  of  a  chemical  lab- 
oratory for  the  Portland  cement  industry  came  to  be  recognized,  and 
as  early  as  the  seventies  every  German  cement  factory  had  a  well- 
founded  laboratory  and  one  or  two  chemists.  The  progress  of  the 
German  cement  industry  is  largely  to  be  attributed  to  the  close  and 
fertile  work  in  these  cement  laboratories.  The  laboratories  offered 
their  services  unselfishly  when  it  was  a  question  of  carrying  out 
scientific  work  for  the  "Association."  Shortly  after  the  establish- 
ment of  the  first  rules  in  1877,  a  committee  was  elected  to  work  out 
new  rules,  and  the  whole  of  the  scientific  work  which  was  necessary 
for  this  purpose  was  done  by  the  chemists  of  the  different  cement 
factories.  How  conscientiously  and  thoroughly  this  was  done  is 
best  proved  by  the  fact  that  the  new  rules  set  up  in  1887  on  the  basis 
of  this  work  were  fully  valid  until  1909;  that  is,  for  more  than  twenty 
years. 

Many  matters  which  are  nowadays  looked  upon  as  self-explanatory 
had  at  that  time  to  be  cleared  up  by  troublesome  and  tedious  experi- 
ments. With  the  growth  of  the  German  Portland  cement  industry, 
constantly  increasing  calls  were  made  by  the  Association  of  German 
Portland  Cement  Makers  on  its  members  for  collaboration  in  tests 
and  chemical  experiments,  especially  after  the  Association  decided  in 
1885  to  watch  permanently  over  the  quality  of  the  German  Portland 
cements.  For  this  purpose  every  cement  had  to  be  bought  in  the 
open  market  at  least  once  a  year  and  submitted  to  the  standard  test. 

With  the  86  different  brands  of  cement  which  existed  in  1898  this 
was  no  small  task,  but  it  was  willingly  done  up  to  that  time  by  a 
few  of  the  large  German  works  free  of  expense  in  the  general  interest. 
You  will  be  interested  to  learn  that  the  chief  reason  for  this  purpose 
was  to  see  that  no  foreign  matter,  such  as  ground  slag  or  limestone, 
was  mixed  in  the  cement  by  works  belonging  to  the  German  Cement 
Association,  which  they  bound  themselves  by  signature  to  refrain 
from  doing. 

Up  to  the  year  1909  there  was  only  allowed  an  addition  of  2  per 
cent,  gypsum  or  coloring-matter  to  regulate  the  setting  time  and  to 
color  the  cement.  The  new  rules  allow  3  per  cent.  And  even  to-day 
every  member  must  bind  himself  by  signature  to  mix  no  kind  of 
foreign  matter  with  his  cement,  on  pain  of  being  expelled  from  the 
Association.  The  Association  of  German  Portland  Cement  Makers 
has  by  this  step  won  in  a  high  degree  the  confidence  of  the  users  of 
cement. 

35 


The  question  became  more  acute  when,  at  the  end  of  the  last 
century,  the  so-called  iron  Portland  cement  works  came  into  existence, 
which  added  30  to  70  per  cent,  of  ground  blast-furnace  slag  to  the 
cement  after  grinding.  New  methods  of  analysis  had  to  be  found 
to  show  in  an  approved  manner  any  adulteration,  and  in  connec- 
tion with  this  a  lot  of  other  work  cropped  up,  which  could  not  all 
be  done  in  the  laboratories  of  the  different  cement  works.  At  the 
same  time  the  Association  was  confronted  with  the  task  of  making 
numerous  tests  for  the  purpose  of  revising  the  rules,  and  the  question 
of  the  constitution  of  Portland  cement  gained  more  interest,  so  the 
building  of  its  own  laboratory  was  decided  on  in  the  year  1899.  The 


Fig.  22. — Laboratory  of  the  Association  of  German  Portland  Cement  Manufac- 
turers at  Carlshorst. 

cost  of  it  was  defrayed  by  each  factory  belonging  to  the  Association 
paying  an  extra  subscription  of  $50  per  share.  Here  I  should  explain 
that  each  factory  has  one  share  and  one  vote  in  the  Association  for 
every  50,000  barrels  production.  A  factory  with  a  production  of 
1,000,000  barrels  has  thus  twenty  shares. 

In  consideration  of  the  meetings  of  the  Association  being  always 
held  at  Berlin,  and  of  the  royal  material  testing  office,  with  which  it 
was  desired  to  collaborate,  being  also  at  Berlin,  it  was  decided  to 
establish  the  laboratory  there.  The  plans  for  the  Association  labora- 
tory were  submitted  to  the  next  general  meeting,  and  the  building 
of  the  same  was  commenced  the  same  year. 

36 


The  building  is  carried  out  in  concrete  and  cement  bricks,  and  it 
is  covered  with  cement  tiles.  On  the  ground  floor  there  is  a  large 
room  for  the  preparation  of  test  matter,  and  a  small  room  for  storing 
the  same.  There  are  also  in  separate  rooms  testing  ovens,  an  electric 
motor,  a  compressor,  and  the  boiler  for  the  steam  heating. 

On  the  first  floor  are  the  rooms  of  the  laboratory  proper,  consisting 
of  a  large  chemical  laboratory,  a  weighing  room,  a  physical  laboratory, 
and  the  room  where  the  testing  matter  is  broken  and  the  cubes  are 
crushed.  Here  is  also  the  manager's  office.  The  second  floor  is 


Fig.  23.— The  Office  of  the  Manager.     The  picture  shows  the  first  President, 

Delbriick. 

built  as  a  dwelling  for  the  laboratory  manager.  The  laboratory  is 
fireproof;  all  the  floors  are  made  of  concrete  and  covered  with  lino- 
leum. Next  to  the  building  is  a  small  shed  for  keeping  the  cements 
in,  and  also  for  storing  the  standard  sand,  which  is  sold  by  the 
Association  laboratory  to  all  factories,  builders,  and  officials.  The 
land  cost  $7000,  the  house  itself  $15,500,  the  shed  $1000,  and  the 
inner  fittings  about  $3000;  altogether,  about  $27,000. 

The  mechanical,  chemical,  and  physical  laboratories  are  fitted 
up  with  all  necessary  apparatus,  but  without  extravagant  equip- 
ment. 

37 


Fig.  24.— The  Chemical  Laboratory. 


Fig.  25.— The  Physical  Laboratory. 

38 


The  laboratory  possesses  further  an  extensive  library,  containing 
all  books  and  papers  on  cement.  A  small  museum  has  also  been  fitted 
up,  in  which  everything  worthy  of  notice  concerning  cement  is 
collected. 

The  " Association  Laboratory"  is  under  a  management-council, 
composed  of  seven  members  of  the  Association  of  German  Portland 
Cement  Makers.  There  are  certain  rules  for  the  management  of  the 
laboratory.  Paragraph  No.  1  says  that  the  laboratory  is  to  serve, 


Fig.  26. — Making  the  Cubes  with  the  Hammer  Apparatus.     On  the  Left  the 

Steinbriick  Mixer. 


in  the  first  place,  for  the  working  out  of  scientific  problems  which  are 
in  the  general  interest  of  the  entire  cement  and  concrete  industry. 

It  is  further  stated  in  the  rules  that  tests  of  chemical  and  physical 
nature  and  breakage  tests  are  to  be  carried  out  against  payment  of 
fixed  fees.  But,  above  all  things,  all  the  German  cements  are  to  be 
bought  by  the  laboratory  as  often  as  possible  from  the  trade,  and 
tested  according  to  the  rules,  whereby  a  check  is  exercised  on  the 
German  cements  by  the  Association.  A  complete  analysis  is  made 
each  year  of  all  German  cements. 

The  management  of  the  laboratory  is  in  the  hands  of  a  chemist, 

39 


who  has  under  him  other  chemists,  laboratory  workers,  and  assis- 
tants. He  has  to  report  every  month  to  the  management-council 
on  the  work  done  in  the  laboratory. 

In  the  reports  to  the  management-council  the  cements  tested  are 
to  be  distinguished  by  numbers  and  not  by  the  names  of  the  factories. 


Fig.  27. — Crushing  the  Cubes  with  the  Amsler-Laffon  PRESS. 

The  strictest  attention  is  given  that  business  interests  shall  in  no 
manner  be  prejudiced  by  the  reports. 

However,  if  it  happens  that  a  cement  does  not  pass  the  standard 
test,  then  the  name  of  the  factory  and  the  tests  are  communicated 
to  the  management-council,  which  then  takes  further  steps.  With 
this  exception  no  factory  learns  anything  of  the  tests  of  the  other 
factories.  On  the  other  hand,  the  manager  of  the  laboratory  com- 

40 


municates  every  year  to  each  factory  the  results  ascertained  in  the 
Association  laboratory  with  its  cement  as  bought  from  the  trade. 
But  no  advertisement  may  be  made  of  these  tests. 

To  ascertain  whether  the  cement  contains  any  foreign  admixture, 
a  special  process,  the  so-called  suspense  analysis,  has  been  worked  out. 
Cements  which  are  at  all  suspected  of  being  adulterated  are  frequently 
bought  from  the  trade  and  tested. 

The  tests  naturally  embrace  also  slag  cements,  foreign  cements, 
natural  cements,  and  iron-Portland  cements,  which  are  regularly 
bought  and  tested. 

I  can  probably  best  give  you  an  idea  of  the  activity  and  utility 
of  the  Association  Laboratory  by  naming  some  of  the  work  which  has 
been  done  in  it  during  the  last  eight  years. 

1.  The  influence  of  a  slight  uncleanness  of  the  standard  sand, 
through  brown  coal  products. 

2.  Regarding  the  Ljamin  methods  of  determining  the  free  hydrate 
of  lime  in  hardened  Portland  cement. 

3.  Analyses  respecting  the  constitution  of  Portland  cement. 

4.  Methods  for  determining  the  free  hydrate  of  lime  in  hardened 
Portland  cement. 

5.  Influence  of  the  addition  of  blast-furnace  slag  to  Portland 
cement. 

6.  Influence  of  the  hardness  of  water  on  the  setting  time  and 
strength  of  cement  mortar. 

7.  Swelling  phenomena  of  Portland  cement  in  distilled  water. 

8.  The  behavior  of  cements  on  the  addition  of  various  means  of 
adulteration,   such   as  trass,   ground  sand,   blast-furnace  slag,   and 
artificial  slag. 

9.  Concerning  the  question  of  mixing  slag. 

10.  Influence  of  ground  water  on  concrete  channels. 

11.  Experiments  regarding  the  permissible  percentage  of  sulphuric 
acid,  made  with  ninety  different  cements. 

12.  Storage  of  cement  bodies  exposed  to  the  weather. 

13.  Testing  process  with  atmospheric  hardening. 

14.  Methods  of  recognizing  foreign  admixtures  in  cement. 

15.  Working  out  of  a  method  for  determining  the  sulphide  sulphur. 

16.  Comparative  strengths  with  different  manners  of  seasoning- 
made  on  over  ninety  cements. 

17.  Testing  of  ninety  cements  with  increased  proportion  of  gypsum. 

18.  Testing  of  ninety  cements  with  combined  atmospheric  and 
water-hardening. 


19.  Finding  of  shortened  ways  of  testing  the  constancy  in  volume 
of  hydraulic  cements. 

20.  Comparative  tests  of  Portland  cements  with  iron-Portland 
cements. 

21.  Comparative  strength  tests  of  "  Association "  cements  with 
different  methods  of  hardening. 

22.  Concrete  experiments  with  different  sands  and  gravels. 

23.  Concrete  experiments  with  ground-damp  and  plastic  mixture. 

24.  Experiments  on  the  setting  of  all  " Association"  cements  in  a 
fresh  state,  and  after  three,  six,  nine,  and  twelve  months'  storage. 

25.  Chemical  analysis  of  sea-water  testing  bodies. 

26.  Uniform  testing  of  hydraulic  cements  by  means  of  prisms. 

27.  Experiments  on  bending,   crushing  and  tensile  strength  of 
prismatic  test  bodies  according  to  Schule  and  Ferret. 

28.  Attempts  to  make  test  bodies  out  of  pure  cement  with  the 
hammer  apparatus. 

29.  Regarding  the  storage  constancy  of  Portland  cement. 

30.  Experiments  with  Belgium  natural  cements. 

31.  Experiments  on  the  calcination  loss  and  the  specific  weights 
of  Portland,  natural,  and  slag  cements. 

32.  Experiments  on  the  water  porosity  of  mortars. 

33.  The  behavior  of  Portland  and  slag  cements  when  hardened 
in  salt  solutions. 

34.  Testing  of  Portland  cement  mortars  with  regard  to  water 
porosity  with  addition  of  ground  limestone,  hydrate  of  lime,  hydraulic 
lime,  and  trass. 

35.  Establishment  of  a  uniform  method  of  analysis  for  Portland 
cement. 

36.  Influence  of  the  proportion  of  sulphide  sulphur  with  atmos- 
pheric hardening. 

37.  The  oxidation  of  sulphide  sulphur  in  iron-Portland  cement. 

38.  Testing    of    mortar  mixtures  of  iron-Portland  cement  with 
pumice  sand. 

39.  Testing  of  all  "  Association "  cements  according  to  the  Le 
Chatelier  test. 

40.  Experiments  on  the  increase  in  temperature  with  the  setting 
of  cement. 

Gentlemen,  this  is  an  extract  from  the  scientific  work  done  in 
recent  years  by  the  "  Association "  laboratory.  The  chief  activity 
of  the  " Association"  laboratory  is  directed  to  the  regular  testing  of 
the  "  Association  "  cements,  to  the  making  of  tests  for  private  parties, 

42 


and  to  work  ordered  by  and  together  with  the  different  commissions 
of  the  Association  of  German  Cement  Makers.  Of  such  commissions 
we  have:  (1)  The  sea- water  committee;  (2)  the  rules  committee; 
(3)  the  sand  committee;  (4)  the  setting  time  committee;  (5)  the 
committee  for  concrete  experiments  in  moorland;  (6)  the  committee 
for  reinforced  concrete. 

For  all  these  committees  the  "  Association "  laboratory  has  to 
carry  out  the  experiments,  which  are  generally  very  comprehensive. 

The  rules  committee  ordered  in  one  year  alone  the  making  of 
14,000  test  bodies.  The  standard  sand  is  also  under  the  supervision 
of  the  "  Association  "  laboratory. 

Within  a  few  years  the  sale  of  standard  sand  has  been  transferred 
to  the  "  Association  "  laboratory,  which  derives  a  considerable  income 
therefrom. 

Besides  this,  the  laboratory  is  being  in  recent  years  more  and 
more  employed  by  the  factories  of  the  "  Association "  and  by  private 
parties.  The  number  of  tests  asked  for  from  this  side  in  the  past  year 
amounted  to  over  500.  Most  of  these  were  tests  according  to  the 
rules,  but  there  were  also  raw  meal  analyses,  suspension  analyses, 
tests  of  trass,  tests  of  concrete,  sand  samples,  oil  samples,  tests  of 
building  bricks,  tests  of  caloric  values,  and  tests  of  feed-water  for 
boilers.  Various  cement  works  have  subscribed  to  have  their  cement 
tested  every  fourteen  days  in  the  "  Association "  laboratory. 

The  cost  of  up-keep  of  the  laboratory  is  covered  by  the  revenue 
from  these  testing  fees,  together  with  the  profit  on  the  sale  of  standard 
sand. 

The  greatest  amount  of  work  done  by  the  laboratory  is,  however, 
the  testing  according  to  rules  of  all  the  brands  of  cement  belonging 
to  the  "  Association,"  the  number  of  which  has  now  risen  to  96. 

Each  cement  is  subjected  to  all  the  tests  prescribed  by  the  rules. 
It  is  tested  for  fineness,  specific  weight,  volume  weight,  setting  time, 
volume  constancy,  tensile  and  crushing  strength  both  with  water- 
hardening  and  combined  atmospheric  and  water  seasoning.  There 
are  further  made  with  each  cement  accelerated  tests  for  volume 
constancy,  including  the  Heinzel  ball  test,  the  kiln  test,  and  the 
boiling  test.  The  last  was  not  passed  in  the  year  1909  by  thirty- 
two  cements,  which  otherwise  were  of  the  best  quality  and  showed 
great  strength.  No  objection  was,  of  course,  made  to  these,  and  the 
boiling  test  is  only  made  to  show  its  uselessness. 

A  complete  analysis  is  also  made  of  each  cement.  In  this  way 
very  abundant  and  valuable  analytic  material  is  obtained,  from  which 

43 


conclusions  can  be  drawn  with  regard  to  the  making  of  a  good  Port- 
land cement.  In  the  year  1909  it  was  ascertained  that  the  mean  lime 
percentage  of  all  German  cement  brands  reached  63.47  per  cent., 
the  highest  point  up  to  that  time.  The  maximum  contained  in  a 
cement  was  as  much  as  66.47  per  cent.  CaO.  It  will  interest  you 
to  know  that  although  the  German  rules  call  for  only  250  kilos  pressure 
strength  at  the  end  of  twenty-eight  days,  more  than  half  of  all  German 
cement  brands  had  350  kilos,  and  of  these  eight  cements  showed  as 
much  as  450  kilos  pressure  strength  at  the  end  of  twenty-eight  days. 

The  annual  results  of  all  cement  tests  arid  analyses  of  all  German 
cements  are  tabulated  and  published  every  five  years  in  a  special 
pamphlet,  which  enables  cement  investigators  to  have  at  their  dis- 
posal very  conscientiously  prepared  and  copious  material.  In  this 
summary  the  various  cement  brands  are,  of  course,  not  designated  by 
names  but  by  numbers. 

Gentlemen,  I  can  to-day  only  draw  for  you  in  bold  lines  a  picture 
of  the  activity  of  the  "  Association"  laboratory;  if  I  went  into  details, 
a  whole  book  could  be  written  about  it,  although  it  has  hardly  been 
ten  years  in  existence.  I  think,  however,  you  will  already  have 
formed  an  idea  as  to  how  very  useful  it  is  to  the  German  cement 
industry.  The  laboratory  would  have  fulfilled  its  purpose  if  it  had 
done  nothing  further  than  supervise  the  quality  of  the  German 
cements.  The  "  Association  "  laboratory  has,  however,  far  exceeded 
the  expectations  that  were  placed  in  it.  At  the  commencement 
there  were,  of  course,  difficulties  to  be  overcome;  the  proper  man 
could  not  be  found  at  the  start  to  manage  it,  and  the  revenue  did 
not  suffice  to  cover  the  expenses.  But  the  laboratory  has  now  stood 
for  a  number  of  years  under  the  management  of  an  able  and  cautious 
chemist,  who  succeeded  in  a  short  time  in  making  the  laboratorj-  pay 
for  itself. 

If  I  have  indicated  to  you  to-day  the  importance  of  this  institu- 
tion, I  have  done  so  with  a  special  intention.  When  I  had  the  oppor- 
tunity last  year  of  studying  the  American  cement  industry,  I  admired 
nearly  everywhere  the  splendid  arrangement  of  the  factories,  and  I 
was  impressed  by  the  fact  that  the  young  American  cement  industry 
had  made  enormous  progress  in  a  short  time.  But  on  the  whole  it 
seemed  strange  to  me  that  here  in  America  so  little  laboratory  work 
is  done  in  the  general  interest  by  the  cement  makers,  and  that  you 
have  no  "  Association "  laboratory,  such  as  has  been  founded  in 
different  countries  after  the  pattern  of  the  German.  Some  of  your 
members  inquired  at  that  time  about  our  "  Association  "  laboratory, 

44 


and  I  therefore  thought  it  would  be  of  interest  to  you  to  learn  some- 
thing about  its  arrangement  and  activity. 

The  preliminary  work  which  was  necessary  for  the  establishment 
of  the  new  German  rules  was  mostly  done  in  the  " Association" 
laboratory,  and  it  was  only  when  the  work  was  sufficiently  advanced 
to  enable  definite  methods  of  testing  to  be  built  up,  that  the  latter 
were  further  worked  out  and  completed  by  the  members  of  the  rules 
committee.  You  all  know  the  new  German  rules  which  have  been 
in  force  since  last  year  for  all  German  states,  but  it  will  interest  you 
to  learn  the  early  history  and  to  hear  the  reasons  which  led  to  the 
fixing  of  the  different  specifications. 

As  I  have  already  mentioned,  rules  for  testing  Portland  cement 
were  first  laid  down  in  1877.  In  the  rules  of  that  time  the  following 
was  determined : 

The  cement  should  be  sold  in  barrels  of  180  kilos  (396  Ibs.).  It 
should  be  constant  in  volume  and  seasoned. 

Cement  which  had  not  set  in  half  an  hour  was  considered  slow 
setting.  Every  cement  should  set  in  two  hours  at  the  most.  The 
fineness  of  grinding  was  fixed  at  20  per  cent,  on  the  900-mesh  sieve, 
which  corresponds  to  your  sieve  No.  100. 

The  cement  was  tested  for  tensile  strength  only,  as  is  to-day  still 
the  case  in  America,  and  the  briquettes  were  rammed  by  hand,  as 
you  do  it  here.  The  tensile  strength  was  to  amount  to  ten  kilos 
per  square  centimeter.  These  rules  were  in  force  in  Germany  until 
1887. 

But  it  was  soon  seen  that  the  tests  made  on  the  basis  of  these  rules 
were  not  reliable.  A  cement  which  was  tested  in  accordance  with  the 
rules  in  six  different  places  gave  six  different  results.  The  reason  of 
the  poor  agreement  was  soon  recognized,  first  in  the  impossibility 
of  ramming  the  briquettes  uniformly  by  hand,  and  in  the  great 
influence  of  the  sand  on  the  strength. 

The  problem  had  now  to  be  solved  to  make  the  testing  procedure 
as  uniform  as  possible,  and  to  eliminate  all  sources  of  error  in  the 
preparation  of  the  samples.  A  sharp,  fine  quartz  sand  of  as  uniform 
a  grain  as  possible  was  first  sought  for.  Such  a  deposit  was  found  at 
Freienwalde,  and  it  was  brought  to  a  definite  fineness  by  screening. 
The  preparation  of  this  standard  sand  is  under  the  control  of  the 
royal  material  testing  office  and  the  "  Association "  laboratory. 

The  elimination  of  the  sources  of  error  could  only  be  obtained 
by  substituting  machinery  for  hand  work,  and  therefore  Steinbrtick's 
mortar-mixer  was  tried  for  mixing  the  mortar,  and  Bohme's  hammer 

45 


apparatus  for  ramming  the  briquettes  in  the  molds.  It  was  also 
attempted  to  regulate  the  addition  of  water.  In  the  meantime  the 
conviction  was  arrived  at  that  the  testing  of  the  concrete  for  pressure 
strength  was  just  as  important  as  for  tensile  strength;  an  apparatus 
was  sought  to  crush  the  cubes,  and  it  was  found  in  the  Amsler  Laffon 
press.  When  the  new  rules  were  introduced  in  the  year  1887,  the 
terms  of  the  same  had  been  so  well  worked  out  by  experiments  that 
they  stood  proof  for  twenty-two  years  with  success.  These  rules, 
which  were  in  force  until  1909,  differed  from  the  old  rules  chiefly  in 
the  following  points : 

1.  A  definition  for  Portland  cement  was  laid  down.     The  object 
of  this  was  to  exclude  from  the  definition  " Portland  cement"  all 
cements  which  had  been  diluted  by  the  admixture  of  blast-furnace 
slag  or  limestone.     The  members  of  the  Association  were  bound  to 
bring  into  the  market  nothing  but  pure,  unmixed  Portland  cement. 
The  declaration  they  had  to  sign  ran:  "The  members  of  the  Associa- 
tion may  only  bring  into  the  market  under  the  designation  of  'Port- 
land cement '  a  product  made  by  an  intimate  mixing  of  finely  ground 
calcareous  and  argillaceous  materials  or  calcareous  and  argillaceous 
silicates  burnt  to  incipient  fusion  and  ground  to  a  flour.     They  bind 
themselves  to  not  acknowledge  as  Portland  cement  any  product  made 
in  a  different  way  from  that  described  above,  or  to  which  foreign 
matter  is  added  during  or  after  burning,  and  to  look  upon  the  sale  of 
such  products  as  deception  of  the  buyer.     But  this  bond  does  not 
apply  to  slight  additions  up  to  the  amount  of  2  per  cent,  which  may 
be  required  for  the  regulation  of  the  setting  time  or  for  other  special 
purposes." 

2.  In  addition  to  tensile  strength,  the  pressure  strength  was  intro- 
duced.    At  the  same  time  the  claims  on  the  strength  were  raised  con- 
siderably, namely  from  10  to  16  kilos  per  square  centimeter.     For 
the  pressure  strength  160  kilos  per  square  centimeter  was  fixed. 

3.  The  standard  sand  was  introduced  as  uniform  sand,  and  the 
preparation  of  the  briquettes  by  machinery  was  determined  on. 

4.  The  residue  permissible  on  the  900-mesh  screen  was  reduced 
from  20  per  cent,  to  10  per  cent. 

5.  The  Vicat  needle  was  introduced  for  the  determination  of  the 
setting  time,  and  it  was  resolved  that  slow-setting  cements  should  have 
at  least  two  hours'  setting  time. 

The  old  rules  regarding  the  volume  constancy  were  retained 
unchanged. 

At  the  commencement  of  this  century  concrete  construction  and 


the  use  of  concrete  for  building  found  a  larger  field;  it  was  soon 
recognized  that  the  claims  on  the  strength  would  again  have  to  be 
increased,  and  that  the  preparation  of  the  test  bodies  would  have  to 
be  more  suited  to  the  practice.  If  with  the  previous  rules  the  season- 
ing in  water  was  laid  down,  it  was  done  because  the  results  agreed 
closest  with  this  method.  In  years  of  work,  in  which  many  hundred 
thousand  sample  bodies  were  stamped  and  crushed  by  members 
of  the  Association,  a  serviceable  method  was  at  last  found  in  the  so- 
called  combined  seasoning,  that  is,  immersion  for  six  days  in  water 
and  then  keeping  for  twenty-one  days  at  room  temperature. 

As  cement  is  now  often  worked  in  a  plastic  condition,  endeavors 
were  made  to  test  sample  bodies  made  of  plastic  cement  mortar. 
But  all  the  results  from  many  thousands  of  experiments  were  insuffi- 
cient. No  conformity  could  be  attained.  So  it  was  decided  to  again 
make  the  briquettes  out  of  ground-damp  cement  mortar  the  same  as 
before.  You  are  aware  that  the  International  Commission  is  trying 
for  the  testing  of  plastic  cement  mortar,  but  according  to  the  results 
yielded  by  the  experiments  in  Germany  it  will  hardly  be  possible, 
especially  if  value  be  placed  on  agreement  in  the  results  of  the  tests, 
which  is  the  chief  thing. 

In  accordance  with  actual  practice,  the  briquettes  have  been  kept 
in  the  open  air,  exposed  to  heat,  cold,  rain,  and  sunshine,  and  tested 
after  twenty-eight  days.  The  degrees  of  strength  ascertained  were 
very  high,  but  did  not  at  all  agree  with  each  other.  This  method  was 
therefore  abandoned. 

Trials  were  then  made  with  simply  leaving  the  samples  to  harden 
at  room  temperature.  But  even  with  this  method  the  tests  made  in 
different  laboratories  did  not  show  the  desired  conformity.  Dr. 
Michaelis  then  proposed  to  imitate  actual  practice  by  placing  the 
samples  alternately  in  cold  water,  in  the  atmosphere,  and  in  a  box 
at  high  temperature,  and  testing  after  twenty-eight  days  of  such 
treatment.  The  results  were  favorable,  and  much  higher  strengths 
were  determined  than  by  immersion  in  water.  In  spite  of  this,  how- 
ever, the  method  was  not  adopted,  owing  to  it  being  so  complicated. 
The  method  proposed  by  Dr.  Goslich  met  the  same  fate;  his  sugges- 
tion was  to  let  the  bodies  harden  in  a  closed  box  over  burnt  lime, 
while  excluding  the  carbonic  acid. 

The  only  serviceable  way  of  seasoning  the  samples  proved  to  be 
the  combined  seasoning,  that  is,  six  days  in  the  water  and  then  twenty- 
one  days  in  the  atmosphere.  This  method  was  again  checked  by  the 
making  and  testing  of  several  thousand  sample  bodies. 

47 


Concrete  work  has  chiefly  to  withstand  pressure,  and  it  was 
therefore  decided  to  meet  the  natural  conditions  in  this  respect, 
and  the  pressure  test  was  introduced  as  the  conclusive  test.  The 
test  for  tensile  strength  is  now  only  of  minor  importance,  and  has 
only  been  retained  as  a  preliminary  test  for  the  building  place.  After 
seven  days'  water  seasoning  the  minimum  strength  shall  be  at  least 
12  kilos  per  square  centimeter. 

As  it  is  often  important  for  the  concrete  builder  to  make  sure  as 
soon  as  possible  of  the  quality  of  the  cement,  this  circumstance  was 
taken  account  of  in  the  new  rules  by  the  introduction  of  a  crushing 
test  after  keeping  the  cube  one  day  in  moist  air  and  six  days  under 
water.  The  crushing  strength  must  amount  to  at  least  120  kilos 
per  square  centimeter. 

As,  however,  with  the  laying  down  of  the  new  rules  it  was  especially 
a  question  of  increasing  the  minimum  strength  after  twenty-eight 
days,  which  up  to  then  had  amounted  to  160  kilos  per  square  centi- 
meter, it  became  necessary  to  test  all  the  German  cements  after  the 
new  combined  seasoning,  and  to  fix  the  minimum  strength  in  ac- 
cordance. The  result  was  that  in  place  of  160  kilos  per  square  centi- 
meter in  force  up  to  that  time,  the  minimum  strength  was  fixed  at 
250  kilos  per  square  centimeter  in  the  new  rules.  Otherwise  the 
only  further  change  made  in  the  new  rules  was  that  the  fineness  of 
the  cement  was  again  increased,  and  not  more  than  5  per  cent,  residue 
allowed  on  the  900-mesh  sieve.  You  will  be  interested  to  hear  that 
in  Germany  the  grinding  is  done  much  finer.  The  residue  on  the 
900-mesh  sieve  in  1909  averaged  1 .39  for  all  the  factories.  Cement  was 
bought  from  the  trade  which  had  only  0.1  per  cent,  residue,  and  was 
thus  very  finely  ground.  Five  per  cent,  magnesia  is  permitted  and 
2.5  per  cent,  sulphuric  acid.  These  limits  were,  of  course,  not  intro- 
duced until  the  conviction  had  been  arrived  at  by  numerous  experi- 
ments that  neither  2.5  per  cent,  sulphuric  anhydride  nor  5  per  cent, 
magnesia  are  in  any  way  harmful  to  the  quality  of  the  cement. 
According  to  the  new  rules,  an  addition  of  3  per  cent,  is  allowed  to 
regulate  the  setting  time,  in  consequence  of  rotary  kiln  cements  often 
requiring  more  gypsum  to  make  them  slow  than  ring  kiln  cements. 
The  new  rules  no  longer  contain  any  stipulation  as  to  when  the  setting 
must  be  finished;  they  propose,  as  of  much  more  importance,  to  fix 
the  commencement  of  the  setting,  which  has  been  put  down  as  one 
hour  at  the  outside.  The  definition  of  Portland  cement  has  been 
drawn  up  very  carefully  in  the  new  rules,  so  that  it  is  impossible  in 
the  future  for  other  hydraulic  cements  to  be  mistaken  for  it.  It  runs: 


Portland  cement  is  a  hydraulic  cement  with  not  less  than  1.7 
parts  in  weight  of  lime  (CaO)  to  1  part  in  weight  of  soluble  silica 
(SiO2)  plus  alumina  (A^Oa)  plus  oxide  of  iron  (Fe2O3)  made  by 
fine  grinding  and  intimate  mixing  of  the  raw  materials,  burning  to 
at  least  incipient  fusion  and  fine  grinding. 

Owing  to  the  tests  for  the  new  German  rules  being  spread  over  a 
number  of  years,  and  to  the  tests  being  made  with  all  the  German 
cements  in  ten  different  places,  the  Association  of  German  Portland 
Cement  Makers  possesses  an  enormous  quantity  of  data  on  results 
of  tests,  which  give  very  interesting  conclusions  as  to  the  behavior 
of  cements  under  different  conditions  of  testing. 


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Average  Crushing  Strength  of  all  German  Cements  During  the  Last  Nine  Years. 


The  96  cements  were  tested  in  twelve  different  testing  stations 
for  both  tension  and  pressure,  according  to  the  old  and  the  new  rules. 
It  turned  out  that  the  results  with  combined  seasoning  agreed  ex- 
cellently. 

The  minimum  of  120  kilos  pressure  strength  was  reached  by 
all  the  cements  with  the  exception  of  three.  I  would  emphasize  the 
fact  that  these  tests  were  made  before  the  new  rules  came  into  force, 
solely  to  ascertain  how  many  cements  at  the  time  of  the  old  rules 
corresponded  to  the  higher  standards  of  the  new  rules.  Nearly  all 
the  cements  already  came  up  to  the  new  standard. 

Only  one  cement  remained  under  160  kilos,  the  standard  of  the 

49 


old  rules,  while  all  cements  with  the  exception  of  seven  showed  over 
200  kilos  pressure  strength,  so  that  it  was  decided  to  take  this  figure 
as  the  minimum  strength.  The  seven  factories  had  therefore  to 
improve  the  quality  of  their  cement  to  reach  at  least  200  kilos  pres- 
sure resisting  strength  after  twenty-eight  days. 

It  is  expressly  stipulated  in  the  new  rules  that  this  manner  of 
testing  with  twenty-eight  days'  water-seasoning  is  only  to  be  applied 
to  those  cements  which  are  to  be  used  for  waterworks.  Otherwise 
the  combined  seasoning  is  taken,  that  is,  six  days  in  water  and  twenty- 
one  days  in  the  air.  As  only  nine  of  the  96  cements  did  not  attain 
a  strength  of  250  kilos  after  twenty-eight  days,  it  was  decided  to 
introduce  250  kilos  as  the  minimum  strength,  in  consideration  that 


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Average  Percentage  of  Lime  in  All  German  Cements  During  the  Last  Nine  Years. 

the  manufacture  of  these  nine  cements  could  be  so  far  improved  as 
to  bring  them  up  to  this  limit.  This  test  for  pressure  resistance  with 
combined  seasoning  is  thus  laid  down  in  the  new  rules  as  the  most 
important  and  conclusive  one.  After  its  introduction  all  German 
cements  passed  the  test  made  last  year  by  the  Association  laboratory. 

In  scientific  interest  all  cements  have  been  tested  in  the  same 
manner  for  tensile  strength. 

It  is  very  interesting  to  see  how  the  average  strength  of  all  the 
German  cements  tested  in  the  Association  laboratory  during  the 
years  1902  to  1909  considerably  increased,  in  view  of  the  probability 
of  the  introduction  of  new  standards. 

The  average  figure  in  1902  was  240  kilos;    then  in  1904,  242 

50 


kilos;  in  the  year  1906,  nearly  249  kilos;  and  after  a  slight  decrease 
in  1907,  it  amounted  to  290  kilos  in  1909  at  the  time  of  the  introduc- 
tion of  the  new  rules.  These  are  the  values  of  the  tests  according 
to  the  rules  valid  at  the  time,  which  only  called  for  160  kilos. 

But  with  the  efforts  constantly  to  make  better  cement,  the  average 
lime  percentage  of  the  German  cements  has  also  considerably  in- 
creased of  late  years,  so  that  it  now  amounts  to  63.4.  You  see  what 
interesting  comparative  material  is  produced  by  the  work  in  the 
"  Association  "  laboratory. 


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Average  Fineness  on  Screen  of  5000  Mesh  per  Square  Centimeter  of  All  German 
Cements  for  the  Last  Nine  Years. 

I  think  that  from  my  remarks  you  will  have  formed  an  idea 
of  the  persistent  and  splendid  manner  in  which  for  years  the  tests 
were  carried  out  and  which  finally  led  to  the  establishment  of  the  new 
German  rules.  A  copious  material,  which  probably  exists  in  no 
other  association  of  cement  makers,  has  been  collected,  making  it 
possible  on  the  basis  of  the  experience  gained  to  establish  new  founda- 
tions for  testing  cement,  which  call  for  a  better  quality  of  cement, 
and  which  are  more  suited  to  actual  practice  than  formerly.  It  is 
therefore  to  be  hoped  that  the  new  German  rules  will  stand  proof 
for  years  and  guarantee  a  satisfactory  testing  of  Portland  cement. 

51 


The  Association   of   American   Portland   Cement    Manufacturers   is   an 
Educational  and  Scientific  Body,  composed  of  the  following  Members: 


ALLENTOWN    PORTLAND    CEMENT 

CO.,  Allentown,  Pa. 

ALMA  CEMENT  CO.,  Wellston,  Ohio. 
ALSEN'S      AMERICAN      PORTLAND 

CEMENT   WORKS,  45   Broadway, 

New  York,  N.  Y. 
AMERICAN   CEMENT   CO.   OF   NEW 

JERSEY,     Pennsylvania     Building, 

Philadelphia,  Pa. 
ASH    GROVE    LIME    &    PORTLAND 

CEMENT  CO*.  R.  A.  Long  Building, 

Kansas  City,  Mo. 
ATLAS  PORTLAND  CEMENT  CO.,  30 

Broad  St.,  New  York,  N.  Y. 
BATH  PORTLAND  CEMENT  CO.,  Bath, 

Pa. 
CALIFORNIA   PORTLAND    CEMENT 

CO.,  Los  Angeles,  Cal. 

CASTALIA  PORTLAND  CEMENT  CO., 

Publication  Building,  Pittsburg,  Pa. 
CAYUGA  LAKE  CEMENT  CO.,  Ithaca, 

N.  Y. 
CHICAGO  PORTLAND  CEMENT  CO., 

1 08  La  Salle  Street,  Chicago,  HI. 
COLORADO  PORTLAND  CEMENT  CO. 

Denver,  Colo. 
CONTINENTAL  PORTLAND  CEMENT 

CO.,  St.  Louis,  Mo. 
COPLAY  CEMENT  MFG.  CO.,  Coplay, 

Pa. 
DEWEY    PORTLAND    CEMENT    CO., 

Scarritt  Building,  Kansas  City,  Mo. 
DEXTER  PORTLAND   CEMENT  CO., 

Nazareth,  Pa. 

DIAMOND  PORTLAND  CEMENT  CO., 
Williamson  Building,  Cleveland,  Ohio. 

DIXIE     PORTLAND     CEMENT     CO., 
Richard  City,  Tenn. 

SDISON  PORTLAND   CEMENT   CO., 

Stewartsville,  N.  J. 
FREDONIA      PORTLAND     CEMENT 

CO.,  Fredonia,  Kansas. 
GERMAN-AMERICAN        PORTLAND 

CEMENT  WORKS,  La  Salle,  III. 

GLENS  FALLS  PORTLAND  CEMENT 

CO.,  Glens  Falls,  N.  Y. 
GREAT      WESTERN       PORTLAND 

CEMENT  CO.,  Kansas  City,  Mo. 
HELDERBERG  CEMENT  CO.,  78  State 

Street,  Albany,  N.  Y. 
HURON    PORTLAND    CEMENT   CO., 

Ford  Building,  Detroit,  Mich. 
IOLA  PORTLAND  CEMENT  CO.,  lola, 

Kansas. 
IOWA  PORTLAND  CEMENT  CO.,  De» 

Moines,  Iowa. 
LAWRENCE  PORTLAND  CEMENT  CO., 

Siegfried,  Pa. 

LOUISVILLE  CEMENT  CO.,Speed*,Ind. 
MARQUETTE    CEMENT    MFG.    CO., 

La  Salle,  III. 
MONARCH  PORTLAND  CEMENT  CO., 

Humboldt,  Kansas. 
NAZARETH  CEMENT  CO.,  Naz«r«th,Pa. 


NEW    AETNA   PORTLAND    CEMENT 

CO.,  Detroit,  Mich. 
NEWAYGO  PORTLAND  CEMENT  CO., 

Grand  Rapids,  Mich. 
NORFOLK       PORTLAND       CEMENT 

CORPORATION,  604  Pennsylvania 

Bldg.,  Philadelphia,  Pa. 
NORTHWESTERN     STATES     PORT- 
LAND CEMENT  CO.,  Mason  City, 

Iowa. 
OGDEN   PORTLAND    CEMENT    CO., 

Ogden,  Utah. 
OKLAHOMA     PORTLAND     CEMENT 

CO.,  Ada,  Oklahoma. 
OMEGA   PORTLAND    CEMENT    CO., 

Jonesville,  Mich. 
PEERLESS  PORTLAND  CEMENT  CO., 

Union  City,  Mich. 
PENINSULAR    PORTLAND    CEMENT 

CO.,  Jackson,  Mich. 
PENNSYLVANIA    CEMENT    CO.,    29 

Broadway,  New  York,  N.  Y. 
PHOENIX  PORTLAND  CEMENT  CO., 

Nazareth,  Pa. 
PORTLAND  CEMENT  COMPANY  OF 

UTAH,  Salt  Lake  City,  Utah. 
RIVERSIDE     PORTLAND      CEMENT 

CO.,  Los  Angeles,  Cal. 
SANDUSKY  PORTLAND  CEMENT  CO., 

Sandusky,  Ohio. 
SECURITY    CEMENT    &    LIME    CO., 

Baltimore,  Md. 

SOUTHWESTERN     STATES     PORT- 
LAND CEMENT  CO.,  Dallas,  Texas. 
STANDARD  PORTLAND  CEMENT  CO., 

Charleston,  S.  C. 
STANDARD     PORTLAND     CEMENT 

CORPORATION,  Crocker  Bldg.,  San 

Francisco,  Cal. 
SUPERIOR  PORTLAND  CEMENT  CO., 

THE,  Cincinnati,  Ohio. 
TEXAS    PORTLAND    CEMENT    CO., 

Cement,  Texas. 
U.    S.    PORTLAND     CEMENT    CO., 

Kansas  City,  Mo. 
UNION    SAND    &    MATERIAL    CO., 

Liggett  Bldg.,  St.  Louis,  Mo. 
UNITED    KANSAS    PORTLAND    CE- 
MENT CO.,  lola,  Kansas. 
UNITED  STATESPORTLAND  CEMENT 

CO.,  Coors  Building,  Denver,  Colo. 
UNIVERSAL     PORTLAND     CEMENT 

CO.,  1x5  Adams  Street,  Chicago,  HI. 
VIRGINIA  PORTLAND  CEMENT  CO., 

5  Nassau  Street,  New  York,  N.  Y. 
VULCANITE  PORTLAND  CEMENT  CO. 

Land  Title  Bldg.,  Philadelphia,  Pa. 
WABASH  PORTLAND  CEMENT  CO., 

Ford  Building,  Detroit,  Mich. 
WESTERN  STATES  PORTLAND  CE- 
MENT CO.,  Jackson,  Mich. 
WHITEHALL    PORTLAND     CEMENT 

CO.,  Land  Title  Bldg.,  Phila.,  Pa. 
WOLVERINE    PORTLAND    CEMENT 

CO.,  Coldwater,  Mich. 

Foreign  Member 

CANADA  CEMENT  CO.,  LTD.,  Mont- 
real, Canada. 


Binder 

j      Gaylord  Brou-  Inc. 
I        Stockton,  Calif. 


M  \  2<)9  f 


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